Condition AZ: h

Associated problems are thought to occur in approximately 70 per cent of patients with the distinct skin markings. These include:

• neurological problems:

– learning difficulties (see entry Learning Disability)

– seizures

– hemimegalencephaly (enlarged brain on one side)

• visual problems (see entry Vision disorders in Childhood):

– retinal pigment abnormalities

– myopia (nearsightedness)

– night blindness

– detached retina

• orthopaedic problems:

– scoliosis

– hemihypertrophy (asymmetry of growth on either side of the body)

• precocious puberty (see entry Premature Sexual Maturation)
• heart abnormalities (see entry Heart Defects).

It is thought the condition occurs due to a change in DNA or chromosomes after the sperm fertilises the egg (a process known as conception).

Hypomelanosis of Ito is present at birth and is usually picked up by a dermatologist, paediatrician or neurologist during the first year of life. Thorough history taking and physical examination with attention to neurological and ophthalmological (eye) problems is necessary to detect any problems.

When a sample of skin cells from a person affected are grown in the laboratory, an abnormal chromosome pattern is found in about one third of affected individuals.

The skin effects of hypomelanosis of Ito do not require treatment. In many cases, the skin may develop pigment (colour) over time and blend in well with normal skin. Skin camouflage creams may be used if children are conscious of their appearance.

Neurological problems, orthopaedic problems and ophthalmological problems will need monitoring by the appropriate specialists and treatment given if necessary. Anti-convulsant medication may be required to control seizures.

The appropriate social and educational support will need to be put in place for children with a learning disability.

Inheritance patterns
This is not an inherited disorder, since the error occurs after conception in one population of cells.

Prenatal diagnosis
This condition is not recurrent (occurring again). Management of future pregnancies should be in families should follow routine guidelines, although detailed ultrasound scanning may provide added reassurance.

HITS (UK) Family Support Group

Tel: 01803 401018 (National Contact)
Tel: 07940 114943 (London Contact)
Website: e-fervour.com/hits

The Group is a network of families, originally established in 1991 and re-established in 1999. It offers support and information through a range of resources including a yahoo group, Facebook page and newsletters. The Group holds an annual family day and, where possible, offers links with other similarly affected families.

Group details last updated February 2013.

The features of HCH may include:

• short stature with an adult height in the range of 128 to 151 cm (4 feet 2 inches to 4 feet 11 inches)
• disproportionate shortening of the arms and legs with short, broad hands and feet
• macrocephaly (large head)
• limitation of elbow extension with increased mobility in other joints
• increased lumbar lordosis (exaggerated curvature at the lower end of the spine)
• joint pain due to abnormal alignment of bones and joints
• mild learning problems – this appears to be a feature in a proportion of people with HCH.

About 70 per cent of people with HCH have a change in the FGFR3 gene on chromosome 4. Changes in this gene also cause achondroplasia. The remaining 30 per cent of those with HCH will either have a so far unrecognised change in the FGFR3 gene or a change in other as yet unidentified genes.

It is not easy to diagnose HCH in very young children and may even be difficult in adults. Diagnosis is made by identifying the features known to appear in HCH together with radiological (X-ray) findings. DNA-based testing may confirm the presence of a change in the FGFR3 gene. The absence of a gene change however does not rule out HCH.

There is no treatment for the underlying cause of HCH. Surgery may be necessary to correct bowing of the legs if this causes symptoms. Physiotherapy may also be helpful if there is joint pain. Surgical limb lengthening can be considered but it is a prolonged process requiring a number of operations. Human growth hormone therapy has been given to some children with HCH, but has not been shown to significantly increase final adult height.

Support is available for children with HCH and their families from a number of organisations. Aids may be required to improve access and to facilitate the use of household, school and workplace equipment.

Inheritance patterns
HCH is inherited in an autosomal dominant manner. The parents of most children with HCH do not have the condition. The gene change which causes HCH seems to occur frequently as a new event (a sporadic mutation). A person with HCH has a 50 per cent chance of having a child with the condition.

Prenatal diagnosis
Chorionic villus sampling or amniocentesis is available if a parent has HCH and a mutation in the FGFR3 gene has been identified. Where the mutation has not been identified, ultrasound scanning is the only method of prenatal testing. Families where HCH has been diagnosed should seek genetic counselling.

Information and support in the UK for hypochondroplasia is provided by the Restricted Growth Association (see entry Restricted Growth).

Although some people with BJHS have little or no trouble, in others, pain can be a recurring or, in some, even a constant problem. This renders them prone to the effects of injury and over-use resulting in acute (short-term) pain on prolonged and unaccustomed exercise. More chronic day-in day-out pain is also seen and may require a variety of measures, which can vary from one person to another in order to control it.

About seven to ten per cent of the population of school-age children has been found to have loose joints and occasional pain in the joints and muscles, especially after exercise or at night. Most children with HMS complain of joint pains in the evening or sometime after exercise. These mostly occur in the knees, ankles or non specifically in the legs. Sometimes the joints may appear to be swollen. Swelling should be treated as with any injury: RICE (rest, ice, compression, and elevation). Young children generally do not like ice, but it can be used with older children. If the joint pain persists, a doctor should be consulted.

Children with HMS often wake up in the night complaining of pain in the legs. For the majority, symptoms will improve as they grow older as their supporting muscles and ligaments get tighter and this is why this used to be called ‘growing pains’ which we now feel does not exist.

Some may need to have physiotherapy, occupational therapy, podiatry and pain management through psychology to help strengthen specific muscles that stabilise joints and cope with their pain. It is important that children continue to exercise and do sport to build up their strength and muscles.

Inheritance patterns
As in most of the heritable disorders of connective tissue, the pattern of inheritance for the BJHS is autosomal dominant. This means that 50 per cent of the offspring may carry the gene for the condition. In BJHS, this does not imply that they will inherit any particular set of symptoms, since many affected people have no ill effects at all. It used to be thought that hypermobility simply represented the upper end of the normal distribution of joint laxity. This view has been challenged as increasing evidence emerges to suggest that it is also a genetic connective tissue disorder, (albeit a relatively mild one) in its own right.

Prenatal diagnosis
If a genetic form of hypermobility is known to affect members of a family, referral for genetic advice or counselling should be sought.

Hypermobility Syndrome Association (HMSA)

Helpline: 033 3011 6388
Email: via website
Website: hypermobility.org

The Association is a Registered Charity in England and Wales No. 1011063 and Scotland No. SC037916.  It provides information and support to those affected by one of the hypermobility syndromes. The Association has a network of support groups throughout the UK, an online forum, and a family programme. 

Group details last reviewed November 2024.

There is no support group for Hyperekplexia in the UK. Families can use Contact’s freephone helpline for advice, information and, where possible, links to other families. To meet other families with disabled children, join Contact’s closed (private) Facebook group.

The main symptom is headache, often with nausea, vomiting, dizziness, or vision difficulties. Sometimes balance can be affected and there may be difficulty in walking and hand coordination. In babies, the head size usually increases and this should be measured. Later, difficulty in raising the eyes to look upwards is seen. In NPH, slowly progressive mental deterioration, shuffling gait and tendency to fall backwards, along with urinary accidents can be seen in elderly people.

The most common causes of hydrocephalus in children are infections such as meningitis, or brain haemorrhage after premature birth, head injury (see entry Brain Injuries), or a brain tumour. Hydrocephalus is a common accompaniment of spina bifida. An uncommon cause in the UK is infection of the baby before birth, such as by toxoplasmosis. The cause of NPH is unclear.

Diagnosis of hydrocephalus follows clinical features such as excessively increasing head circumference in babies, headaches, vomiting. A CT scan or MRI will then determine whether the ventricles in the brain are too large, or if there is another cause.

Treatment is usually by insertion of a ‘shunt’ (a small tube -like device) to redirect the excess CSF to the abdomen or, less commonly, the heart. In some cases, a third ventriculostomy can be performed; this involves a tube called an endoscope being inserted into the brain and a hole being made in the floor of the third ventricle to allow CSF flow to resume. This operation avoids the use of a shunt but it is suitable only for certain types of hydrocephalus, and it is not as successful when carried out in babies. Symptoms caused by raised pressure usually improve after treatment, but other signs of brain damage may remain including subtle learning difficulties (see entry Learning Disability) and poor coordination. In NPH, considerable improvement is sometimes seen after shunting.

Shunts sometimes need to be surgically revised due to blockage or infection. Blockage can lead to return of the hydrocephalus symptoms. Shunts usually have fixed pressure settings and sometimes need an operation to change the shunt for a different setting. This can be avoided by insertion of an adjustable shunt that can be changed from the outside using a special magnet.

Shunt infection usually leads to shunt blockage, which has the symptoms mentioned above, but may also be accompanied by fever, abdominal pain and redness or swelling over the shunt catheter. Chronic infection may cause gradual deterioration in overall performance. In shunts draining into the heart, the symptoms are different and more complex, but a blood test is available for diagnosis. The risk of shunt infection has been considerably reduced by the use of antimicrobial shunts that resist infection.

Medical advice should be sought immediately in cases of mental or physical deterioration in those with shunts, or if a shunt blockage or infection is suspected.

Inheritance patterns
Inherited hydrocephalus is very rare, and is usually X-linked, meaning that only boys are affected. It is usually accompanied by abduction of the thumbs. Diagnosis is determined by genetic tests.

Prenatal diagnosis
Often, but not always, seen prenatally on ultrasound. Fetal scanning by magnetic resonance imaging (MRI) is recommended where hydrocephalus is suspected.

Information and support in the UK for hydrocephalus is provided by SHINE (Spina Bifida • Hydrocephalus • Information • Networking • Equality; see entry Spina Bifida).

The head may be abnormally small, of normal size, or large. Sometimes there may be an excessive rate of head growth and it may be appropriate to insert a shunt system for hydrocephalus to prevent the development of a very large head. Babies with hydranencephaly normally show no visual behaviour or other developmental progress. The life span is usually limited to weeks or months but is sometimes longer. Those who are most severely affected may die at birth.

The above description is of severe or true hydranencephaly. Some babies have more surviving brain tissue and may, therefore, have some developmental progress and a longer life span.

Despite the severity of the damage, there is often no clear event in the pregnancy to account for it. There may be a reduction in fetal movements but the mother is often quite unaware of any problem. Recognised causes of this condition include intrauterine death of a twin, or blood loss from the baby by a number of possible mechanisms. A number of acute illnesses or injuries to the mother in pregnancy have been reported in the medical literature in a small number of instances but this is uncommon. Ultrasound late in pregnancy can show the abnormality but may only be performed in high-risk situations. Sometimes a similar situation may occur as a result of severe damage during or immediately after birth but the acute brain illness is then obvious.

Sometimes, where the birth was slow, it may be mistakenly thought that the damage occurred at birth.

Despite the severity of the brain defect, the baby may apparently behave normally at birth with spontaneous limb movements, crying and sucking. Others are unwell with spasticity and feeding and temperature regulation problems.

Epileptic seizures (see entry Epilepsy) are quite common and may not respond to treatment.

Diagnosis of the condition is made by ultrasound of the head. In severe cases, the EEG shows no activity.

Inheritance patterns
This is regarded as an acquired disorder and not genetic. A small number of families have had more than one baby with the disorder. It occurs equally in boys and girls. Counselling is therefore directed to looking for obstetric factors which might be identifiable and remediable. However, this is, in the main, a sporadic disorder with a low risk of recurrence.

Prenatal diagnosis
Late ultrasound in utero may find the abnormality.

There is no support group for hydranencephaly in the UK. Cross-referrals to other entries in Contact’s directory are intended to provide relevant support for these particular features of the disorder. Organisations identified in these entries do not provide support specifically for hydranencephaly.

A support group outside of the UK exists for hydranencephaly. Please ring our helpline for details.

Families can use Contact’s freephone helpline for advice, information and, where possible, links to other families. To meet other families with disabled children, join Contact’s closed (private) Facebook group.

Huntington’s Disease Association

Tel: 0151 331 5444
Email: [email protected]
Website: hda.org.uk

The Association is a Registered Charity in England and Wales No. 296453. It provides information and support to families affected by Huntington’s disease, and runs local branches and groups throughout the UK.

Group details last reviewed June 2024.

Huntington’s Disease Association of Northern Ireland

Tel: 073 4196 3264
Email: [email protected]
Website: hdani.org.uk

The Association is a registered charity in Northern Ireland np. NIC104676, established in 1976. It offers support, information and care for families affected by the condition. It also promotes research and knowledge about the condition. It has information available and a dedicated youth officer. The Association responds to the needs of more than 240 families.

Group details last updated June 2024.

Scottish Huntington’s Association

Tel: 0141 848 0308
Email: [email protected]
Website: hdscotland.org

The Association is a Registered Charity in Scotland No. SC010985. It provides information and support for families affected by Huntington’s disease (HD). The Association offers nine specialist HD services in Scotland, and has four specialist youth advisors. It supports a network of family branches which are run by family members for family members and provide information and peer support. 

Group details last reviewed June 2024.

APS Support UK

Tel: 0300 323 9943
Email: [email protected]
Website: aps-support.org.uk

The Foundation is a Registered Charity in England and Wales No. 1138116.  It provides information and support to anyone affected by Hughes Syndrome and antiphospholipid syndrome.

Group details last reviewed June 2024.

Heart defects

At least 75% of people affected by HOS have heart defects. The most common problem is a defect in the muscular wall (septum) that separates the right and left sides of the heart. A hole in the septum between the upper chambers of the heart (atria) is called an atrial septal defect (ASD), and a hole in the septum between the lower chambers of the heart (ventricles) is called a ventricular septal defect (VSD), but other congenital (occurring at birth) heart defects can occur. Cardiac conduction disease, where the electrical signals that cause the heart to beat are abnormal, such as a slower-than-normal heart rate (bradycardia) or a rapid and uncoordinated contraction of the heart muscle (fibrillation) can also occur. Cardiac conduction problems or arrhythmias may be the only problem with the heart.

Upper limb abnormalities

Abnormalities affect both arms but not necessarily in the same way. The limb defects in HOS are characteristically asymmetrical (not the same on both sides). At least one abnormality in the bones of the wrist (carpal bones) is present in affected individuals. The thumb is usually abnormal (triphalangeal – with three bones, like a finger), absent or underdeveloped. The forearms may be short or absent. The shoulders are usually narrow and sloping. The mildest signs are abnormal bending of the fifth finger and limited rotation of the joints of the forearms which allow the palms of the hands to face up. The most severe involve absence of all or part of the upper limb. These abnormalities may lead to early arthritis.

Sometimes the chest wall is affected, causing funnel or pigeon chest. The lower limbs are not involved and no other abnormalities, apart from those described above, are seen in HOS.

Mutations of the TBX5 gene cause HOS. This gene provides instructions for making a protein that plays a role in the development of the heart and upper limbs before birth. Another gene called SALL4 from the same gene pathway causes Okihiro syndrome, which is very similar to HOS.

The particular pattern of heart defects and upper limb abnormalities will suggest a diagnosis of HOS. X-rays may be needed to assess the abnormalities in the limbs. Echocardiography, imaging of the heart, may reveal heart defects. Conduction disturbances are often seen on electrocardiography (ECG), a test that monitors the electrical activity of the heart. A molecular genetic test on DNA from a blood sample can be used to confirm the diagnosis by finding a mutation in the TBX5 gene.

Surgical correction of heart defects may be possible in some cases. Cardiac conduction disease can be treated with medication or a pacemaker to control the heart rhythm. Occupational therapy, splinting and surgery may be required to improve limb function and a hand surgeon should be consulted to devise a care plan.

Inheritance patterns

HOS is inherited by autosomal dominant inheritance. This means an affected parent has a 50% risk of having an affected child. Because the severity is very variable, a mildly affected parent may have a severely affected child. Unaffected relatives are not at risk of having an affected child.

Prenatal diagnosis

In families where the specific gene mutation has been identified, genetic prenatal diagnosis may be available. This is carried out by testing DNA from the pregnancy via chorionic villus sampling or amniocentesis.

There is no support group for Holt-Oram syndrome in the UK. Families can use Contact’s freephone helpline for advice, information and, where possible, links to other families. To meet other families with disabled children, join Contact’s closed (private) Facebook group.

Support specifically for the upper limb abnormalities of Holt-Oram syndrome is also available from Reach (see entry Upper Limb Abnormalities).

In the most severe form, alobar HPE, those who survive have profound learning disabilities, but they usually acquire some basic developmental skills such as visual tracking, responding to sound, smiling, and evidence of memory. Most children with alobar HPE will have seizures requiring anticonvulsant medication. Muscle spasticity and periods of marked irritability are present to some degree in all, and various medications may be helpful. Episodes of irregular breathing and pulse rate and highly variable body temperature control can be particularly troublesome. Endocrine problems due to pituitary gland malfunction may require medication. Feeding is a major problem, and tube or gastrostomy feeding is often recommended. Constipation is a common problem but can be managed successfully.

In the less severe forms, semilobar and lobar HPE, there is more complete development of the brain into right and left hemispheres. In general, survival is longer than with the alobar type, with many affected children living into adulthood, although early death is also common. Some degree of learning disability is the rule and is often severe. These more severely affected children will have many of the same problems found with alobar HPE. With the mildest forms of lobar HPE, the child may have minimal disability and a normal lifespan.

Associated malformation of the face is often present, most commonly with the alobar type of HPE. Cyclopia, median cleft lip and/or single nostril are markers of the severe end of the spectrum. Absent sense of smell and single maxillary central incisor tooth may be the only facial features at the mild end of the spectrum.

Inheritance patterns
HPE has many different causes. In most instances it is only one feature of a multiple malformation or chromosomal anomaly syndrome (particularly trisomy 13 Patau syndrome).

When it is an isolated malformation or accompanied only by face malformation it may be caused by an abnormal dominant gene (several different dominant genes have now been identified, but more remain to be discovered). It has also occurred among the offspring of mothers with insulin-dependent diabetes mellitus or severe alcohol abuse.

Prenatal diagnosis 
Prenatal detection of alobar HPE is possible by targeted ultrasound examination. The milder forms of HPE may not be evident by prenatal ultrasound examination.

There is no support group for holoprosencephaly in the UK. A support group outside of the UK exists for holoprosencephaly. Please ring our helpline for details.

Families can use Contact’s freephone helpline for advice, information and, where possible, links to other families. To meet other families with disabled children, join Contact’s closed (private) Facebook group.

The complications of HIV infection and the ways infected children may present are numerous and extremely variable. All the systems of the body may be involved including the gastro-intestinal tract, the lungs and the nervous system. They are also prone to develop recurrent infections and some malignancies.

HIV can be transmitted by unprotected sexual intercourse, both homosexual and heterosexual, by the administration of contaminated blood products and by contact with infected needles. HIV infected women can also pass the infection to their unborn children. This may occur while the baby is in utero (in the womb), at the time of delivery, or transmitted by breast milk.

HIV is diagnosed by the presence of antibodies against the HIV virus in the blood. In some cases, tests are only sensitive enough to detect antibodies a few months after the risk of infection.

Current knowledge now encourages HIV testing during pregnancy. Combination antiretroviral therapy in pregnancy and bottle-feeding has reduced the chance of a baby being infected from over 20 per cent down to less than one per cent.

The outlook for children born with the virus has dramatically improved with the introduction of combination antiretroviral therapy. Using a combination of three types of antiretroviral therapy has also led to an improved outcome for infected children.

Most children receiving antiretroviral drugs to reduce the effect of the virus remain very well, attend school and lead normal lives apart from taking medication every day. Children with HIV should receive the normal schedule of vaccinations apart from BCG (a vaccine against tuberculosis).

Inheritance patterns
None. However, the disease may be passed from mother to child during pregnancy or birth.

Prenatal diagnosis
All women are now actively encouraged to have an HIV test in pregnancy as part of routine clinical care. Postnatal tests are available for babies born to HIV positive women.

Waverley Care

Tel: 0131 558 1425
Email: via website
Website: waverleycare.org

Waverley Care is a Registered Charity in Scotland No. SC036500. It provides information, support and services to people in Scotland who are living with HIV or Hepatitis C, including services for children, young people and families. 

Group details last updated January 2016.

Other organisations providing excellent support and information covering HIV Infection/AIDS but not specially geared to children are listed below:

Positively UK

Helpline: 020 7713 0444
Email: [email protected]
Website: positivelyuk.org

The Organisation is a Registered Charity in England and Wales No. 1007685. It provides peer-led support, advocacy and information to women, men and young people living with HIV. 

Group details last updated December 2014.

Terrence Higgins Trust (THT)

Helpline: 0808 802 1221
Email: [email protected]
Website: tht.org.uk

The Trust is a Registered Charity in England and Wales No. 288527. It provides information and support to anyone living with, affected by, or concerned about HIV and other sexually transmitted infections. The Trust runs services from its centres across the UK. 

Group details last updated December 2014.

LCH may occur at any age. It is very variable, ranging from limited skin rashes or bone changes to a severe illness involving many organs, including the brain. The pituitary gland, which controls water balance is often affected, so that patients may drink large volumes of liquid and pass dilute urine. Children may not grow because of a lack of growth hormone.

HLH is a severe disease commonly triggered by infections, with symptoms depending on the infection, but patients are often very ill with a high fever. Patients may bleed or become very anaemic because of damage to the bone marrow.

Rosai-Dorman disease presents with swelling of lymph nodes (typically in the neck). There may be general ill health with fever and changes in the blood cell numbers (cell count).

Fifty per cent of LCH tissue samples have a mutation in a gene (called BRAF^V600E). Related mutations are usually present in the BRAF^V600E negative cases. These mutations cause the proliferation of Langerhans cells.

Primary HLH, which occurs in very young children, is an inherited disorder with mutations in genes affecting the function of white blood cells. Secondary HLH occurs in association with other inherited abnormalities of immunity, in patients with tumours or those receiving immunosuppressive treatment.

Blood tests, examination of a tissue sample (biopsy), scans, x-rays and bone marrow or lumbar puncture may be performed. Diagnosis of LCH or HLH may be confirmed by genetic tests for mutations known to cause these diseases.

Localised LCH may be treated with corticosteroids or surgery. More extensive disease is treated with combinations of cytotoxic drugs such as vinblastine, vincristine, etoposide (VP-16), methotrexate, cytosine arabinoside (Ara-C) and 6-MP. The use of Vemurafenib, which targets BRAF^V600E, is being explored.

HLH is often triggered by infections, which are treated. Children with primary HLH usually require drug treatment with corticosteroids, cytotoxic chemotherapy or immunosuppressive drugs. Once the disease is under control, children with primary HLH generally receive a bone marrow transplant. Secondary HLH is controlled by treating the causes of the disease, but recurrent severe disease may require bone marrow transplantation.

Rosai-Dorfman disease may need treatment with steroids or cytotoxic drugs.

Inheritance patterns
LCH and Rosai-Dorfman are not inherited. Most primary HLH cases have an autosomal pattern of inheritance (one copy of a defective gene is inherited from each parent) and the disease is therefore more common in marriages between relatives. Secondary HLH patients may inherit mutations that predispose them to the disease.

Prenatal diagnosis
Prenatal diagnosis of HLH during pregnancy is possible if a genetic lesion has been identified in a previous affected child.

Histiocytosis UK (Histio UK)

Tel: 07850 740 241
Email: [email protected]
Website: histiouk.org

The Group is a National Registered Charity; No. 1158789. It provides information and support to individuals and families affected by histiocytic disorders. Histio UK promotes and funds scientific research into histiocytosis diseases, Langerhans’ Cell Histiocytosis and Haemophagocytic Lymphohistiocytosis.

Group details last updated August 2016.

In most children, HD becomes apparent during the first few days of life. The major symptoms in a newborn baby are delayed first bowel movement (also called meconium stools), abdominal distension (enlargement or ballooning of the tummy), chronic constipation (inability to pass stools), and reluctance to feed. Babies with HD may also suffer from inflammation of the bowel lining, which may be associated with fever, diarrhoea, blood in the stools and anaemia (a shortage of red blood cells). They may grow and develop more slowly than other babies.

Older children may experience constipation alternating with bouts of diarrhoea, vomiting, pain and anaemia.

The length of colon affected can vary from child to child. Short-segment HD involves up to a third of the large intestine and long-segment HD involves more than one third, possibly the whole colon. Seventy per cent of individuals have short segment HD. The severity of the symptoms is not always consistent with the length of the intestinal segment involved but children with the whole colon involved tend to have more severe symptoms.

In HD, ganglion cells are missing (aganglionosis) from the very end of the large bowel (anal sphincter and rectum) and in a variable part of the colon above this. This part of the bowel fails to function resulting in symptoms of intestinal obstruction.

HD develops in children before they are born (congenital) and appears to be due to genetic factors. A number of genes, for example RET, have been implicated but the genetics is complicated. HD is not caused by anything the mother did while pregnant.

HD diagnosis is confirmed with a rectal biopsy. This involves taking a small biopsy (piece of tissue) from the wall of the last part of the large bowel (rectum) to confirm the absence of ganglion cells.

If HD is not treated, stool can fill the large intestine causing problems such as infection, bursting of the colon and in some cases this can be life-threatening. Individuals diagnosed with HD require early surgery. Rectal washouts may be used to keep the bowel empty before surgery is done. Surgery essentially involves removal of the aganglionic segment and rejoining of the remaining bowel (‘pull-through’ procedure). The surgery is usually effective in relieving the obstruction caused by HD and most children with HD may lead near normal lives thereafter. In children where there are no ganglia in the whole bowel artificial feeding or consideration for intestinal transplantation may be required. Drug therapy is not effective for HD. 

Inheritance patterns
In the majority of HD it occurs sporadically without any family history and as an isolated condition (no other medical problems identified). In about 25 to 40 per cent HD appears to be a familial disease (tends to occur among members of a family), but as discussed is not inherited in a simply described manner.

Prenatal diagnosis
None at present.

Families can use Contact’s freephone helpline for advice and information. You can also connect with other families in our closed Facebook group

Herpes Viruses Association

Helpline: 0845 123 2305
Email: [email protected]
Website: herpes.org.uk

The Association is a Registered Charity in England and Wales No. 291657. It provides information and support to those who have symptoms of herpes viruses, and to the public and medical profession. 

Group details last reviewed June 2024.

The symptoms can be varied and depend on the site of the clot in the body. Clots interfere with normal blood flow by completely or partly obstructing vessels. This leads to a build-up of blood before the clot (in an artery) or behind the clot (in a vein) causing pain and swelling of the tissue around the area. Clots deprive tissues and organs of oxygen and nutrition and may cause permanent damage particularly if the clot obstructs a vital organ, such as in certain parts of the brain or heart. They may grow very quickly and can break apart sending small pieces of the clot (known as emboli) through the blood stream. These emboli can then become lodged in smaller vessels distant from the clot of origin. An emboli lodging within vessels of the lung is known as a pulmonary embolus. By blocking the blood to the lung and depriving the body of oxygen, they may be rapidly life threatening. An emboli lodging in brain vessels can cause a stroke. These are serious conditions which may be associated with a high risk of disablement. Consequently, thrombotic events may require immediate medical attention and appropriate treatment.

Factor V Leiden

In the most common form of inherited thrombophilia, factor V Leiden, the leg may become swollen, painful and red. In some individuals, part of the clot may be dislodged and flow to the lung (pulmonary embolism) which may make breathing difficult. Depending on the size of the blood clot, some individuals may experience severe respiratory difficulty whereas in others breathing problems may be barely noticeable. In very rare cases, a clot might occur in the arm, brain, or liver. Since clots associated with factor V Leiden form in the veins (which take blood to the heart), there is no increased risk of coronary occlusion. However, pregnancy loss and other obstetric complications may occur at an increased rate in women with factor V Leiden. It is important to look for the presence of factor V Leiden in women who experience recurrent miscarriages as it can be treated to reduce the risk of these events occurring.

Factor V Leiden is associated with a change in the factor V gene, otherwise known as factor V Leiden mutation. The factor V gene codes for a coagulant protein. A ‘Leiden’ mutation (or change) in the factor V gene may lead to an increased tendency to develop an inappropriate blood clot. The first blood clot usually occurs in adulthood (approximately 45 years) but may occur in premature babies, neonates and pregnant women. The risk of developing a clot is thought to increase with age. Factor V Leiden is associated with both deep and superficial blood clots in the legs (venous thromboses).

The clotting process (otherwise known as haemostasis) functions as a careful balance between flowing and stopping; and between clotting and dissolving/reabsorbing clots. The consistency of blood is regulated and maintained by the careful balance of a number of different proteins; some of which are involved in coagulation (clot forming) and some of which are involved in the prevention of clot formation and anticoagulation or fibrinolysis (dissolving of formed clots). Thrombophilia may occur in association with abnormalities in either coagulation or anticoagulation proteins.

Specific genes are known to code for coagulation and anticoagulation proteins. Individuals who inherit changes (or mutations) in these genes may have an increased risk or ‘predisposition’ to developing thrombophilia compared to the rest of the population. However, in certain individuals there may only be a small increased risk to health. Other people who have inherited a predisposition to thrombophilia will not experience any symptoms and will remain healthy and unaffected. In particular, the predisposition to forming a thrombosis may be of relevance to our lifestyles as for example the increased risk to air travellers.

Doctors may suspect an inherited predisposition to blood clotting in individuals who have a blocked blood vessel at a young age, or have recurrent thromboses, or have a strong family history of clotting disorders (such as stroke, pulmonary embolism, or deep vein thrombosis). A diagnosis may be made by screening for inherited blood-clotting factors which are known as factor V Leiden and prothrombin gene mutation. Screening for these genetic changes should form part of the routine investigations for individuals who present with thromboses.

Inheritance patterns
Factor V Leiden is inherited as an autosomal dominant trait. However, in some cases, factor V Leiden may be increased as an autosomal recessive trait. This is associated with a greater risk of venous thrombosis.

Prenatal diagnosis 
Prenatal testing is not routinely available.

Prothrombin gene mutations

The prothrombin gene is responsible for the production of a protein, which helps the blood to clot. A change (or mutation) in the prothrombin gene may lead to an increased tendency to develop an inappropriate blood clot. Clinically this may manifest in a similar manner to patients with factor V Leiden. Again, the risk of thrombosis is heightened in pregnancy. This condition is associated with an increased risk of venous thrombosis, blood clots in the legs and lungs (pulmonary embolism), but most frequently in the deep veins of the lower extremities. Blood clots may occur in the head (cerebral vein thrombosis). However, clots may also occur in unusual sites, particularly cerebral sinus vein thrombosis.

Inheritance patterns
Prothrombin is inherited as an autosomal recessive trait. Individuals with a mutation in both prothrombin genes, one on each chromosome, are called homozygous and they appear more likely than heterozygotes (one mutated gene and one normal gene) to develop thrombosis.

Prenatal diagnosis
Prenatal testing is not routinely available.

There is no support group for hereditary thrombophilia in the UK. Cross referrals to other entries in Contact’s directory are intended to provide relevant support for those particular features of the disorder. Organisations identified in those entries do not provide support specifically for hereditary thrombophilia.

Families can use Contact’s freephone helpline for advice, information and, where possible, links to other families. To meet other families with disabled children, join Contact’s closed (private) Facebook group.

Exostoses grow throughout childhood, but usually become fully bony and stop growing at the end of teenage years. When they grow large, they are frequently painful and can disturb growth resulting in variable short height and bone deformity which might need to be corrected.

Less commonly symptoms occur when exostoses press on nearby nerves and blood vessels. Forearm pain, hip, knee and walking problems may occur and flat foot may also exist. Extremely rarely, exostoses may become cancerous. Rapidly-growing and painful exostoses in late adolescence or adulthood with a cartilage-cap thickness in excess of 10mm are usually those with this potential.

The gene responsible for 50% of affected families is EXT1 located on chromosome 8 and causes a slightly more severe form of HME. The EXT2 gene is located on chromosome 11 and is responsible for about 30% of HME. Other genes may be responsible for the remainder of families.

Usually children will be born to families in which HME is already known. Less commonly a child is born with no parents affected. The average age at which HME is diagnosed in childhood is four years, usually by the presence of one or more new bony lumps that are identified on an X-ray. A single exostosis is usually not due to HME.

Surgery to remove problematic exostoses is often required during childhood. In childhood, regular review by an orthopaedic surgeon is recommended (perhaps annually or every second year). A specialist exostosis clinic which takes national referrals occurs at the Royal Hospital for Sick Children in Edinburgh every three months. No other specialist exostosis clinic is known to exist in the United Kingdom. In adulthood, an affected person may still require occasional monitoring by an orthopaedic specialist.

Inheritance patterns
Autosomal dominant. Up to one third of affected individuals represent new gene mutations in whom neither parent has the condition.

Prenatal diagnosis
A prenatal ultrasound will not identify babies at risk. Prenatal or family gene testing is occasionally available through consultation with a consultant clinical geneticist.

HME Support Group

Email: [email protected]

The Group is a Registered Charity in England and Wales No. 1091069. It provides information and support to anyone affected by Hereditary Multiple Exostoses, and offers linking with other families where possible. 

Group details last updated May 2016.

Most people affected by HHT experience two problems:

• the fragile blood vessels are prone to bleed, for example, in the nose causing nose bleeds, and less frequently in the gut. Generally, this bleeding settles down on its own, but if it leads to anaemia, it may need treatment with iron tablets, or with a blood transfusion if severe
• the abnormal blood vessels may become visible as blood spots, for example on the lips or fingertips.

A few people will have abnormal vessels elsewhere. The lungs are affected in 1 in 5 individuals with HHT and it is important that this is recognised (see below). For other sites, such as the liver and brain, it is not clear that any specific tests or treatment are needed if they are not causing problems already.

About 1 in 5 individuals with HHT develops abnormal vessels in the lungs. These are called pulmonary arteriovenous malformations (PAVMs). These malformations let blood bypass or ‘shunt’ past the lung airsacs. They are particularly important because individuals who have PAVMs are at risk of having a ministroke or brain abscess even if they feel well. In addition, a few women with PAVMs have complications during pregnancy. It is therefore important to check whether or not PAVMs are present and, if so, arrange for a simple treatment to close them off.

Inheritance patterns
Autosomal dominant. The earliest sign of HHT in children is usually nose bleeds, but nose bleeds may not develop until middle age. Because HHT may not become apparent until late in life, we are unable to say that younger members of a family are definitely unaffected. It is sensible for their medical records to include the fact that they have a parent with HHT, and for them to be screened for lung involvement.

Prenatal diagnosis 
This is possible in families where a genetic change has been identified.

Telangiectasia Self Help Group

Tel: 01494 528 047
Email: [email protected]
Website: telangiectasia.co.uk

The Group was established in 1985. It offers contact with others affected by the condition where possible. The Group has over 600 members, publishes a periodic newsletter and has information available.

Group details last updated September 2014.

Symptoms of HSP include:

• painful, occasionally swollen joints
• purpura (red/purple skin rash, which fails to go white with pressure)
• abdominal (tummy) pain
• kidney inflammation (see entry Glomerulonephritis).

Generalised abdominal pain may be caused by inflammation and swelling of the wall of the intestines or, more rarely, by a twisting inversion of the lining of the large intestine (bowel), which is called an acute intussusception.

HSP usually occurs after an infection, often a viral respiratory tract infection and is due to an abnormal response of the immune system. It is unclear why this occurs.

Examination of the skin will reveal the typical rash seen in HSP that starts in the feet and can involve the legs, trunk and arms. Joint tenderness will also be clear from a physical examination. In some cases, a skin biopsy, removal of a small piece of skin tissue for analysis, may be required. A urine sample may be tested to look for haematuria (blood) and proteinuria (protein) in the urine. Blood and protein get into the urine because of the involvement of the kidneys in HSP. Abdominal involvement may be investigated by a CT scan.

The natural course of the disease in children is to settle and not return. There is no specific treatment. Most cases go away on their own without treatment. If symptoms persist, corticosteroids, such as prednisone, may be required. Steroids dampen down the response of the immune system and will improve symptoms. If acute intussusception occurs then surgery may be necessary to correct this. Rarely other treatments are required if the disease is severe or if attacks of disease keep recurring. This is more common in adolescents and adults.

Whilst kidney involvement is common, occurring in up to 60 per cent of sufferers, serious kidney damage is very uncommon. Haematuria may persist for months if regular urine testing is performed. If kidney involvement is severe or if it persists, a kidney biopsy may be performed.

Recurrent HSP may recur in association with subsequent infections. However, the chance of a full recovery is excellent.

Inheritance patterns
None.

Prenatal diagnosis
None.

Henoch Schonlein Purpura Support Group

Tel: 0118 9416 391
Email: [email protected]

Contact a Family – this is a small contact group, established in 2003. It offers a listening ear and relates experiences of parents who children have been affected by the condition. 

Group details last updated January 2023.