Also known as: Diastrophic Dwarfism
Diastrophic dysplasia (DTD) is a rare, inherited skeletal dysplasia, a condition of abnormal bone growth or development, affecting both females and males. It results in restricted growth, curving of the spine called scoliosis and abnormalities of the fingers and toes. People affected by DTD have normal intelligence. Approximately 1 in 110,000 babies born are thought to be affected by DTD.
Medical text written January 2005 by Contact a Family. Approved January 2005 by Dr M Wright. Last updated November 2012 by Dr M Wright, Consultant Clinical Geneticist, Institute of Medical Genetics, International Centre for Life, Newcastle upon Tyne, UK.
The ways and severity that individuals with DTD are affected vary. The features of DTD include:
- shortening of the limbs but with a normal sized skull. The average height of adults is 118cm (for males it is: 86 to 127cm; and for females 104 to 122cm)
- small chest
- cleft palate in about 33 per cent of cases (see entry Cleft Lip and/or Palate)
- swelling of the ears giving a ‘cauliflower’ appearance
- joint contractures – progressive lack of mobility of joint due to changes in the soft tissues
- shortening of the bones of the hands including hitchhiker thumbs (short bones cause the thumb to take up the typical hitchhiker position)
- club feet (see entry Congenital Talipes Equinovarus), varying from mild-to-severe due to bone abnormalities
- progressive scoliosis (sideways curvature of the spine), lumbar lordosis (forward curvature of the lower spine) and cervical kyphosis (outward curvature of the upper spine)
- Breathing complications can occur in infancy and in some cases can be life-threatening.
DTD is a genetic condition. It is caused bya change in the DNA (a mutation) on the SLC26A2 (DTDST) gene on chromosome 5.
DTD is diagnosed by recognition of the clinical features of the condition, such as short stature, club foot and scoliosis and by assessment of X-rays. Molecular testing (testing DNA) of the SLC26A2 gene can confirm the diagnosis if the mutation known to cause DTD is found.
Treatment for DTD will help to relieve symptoms for specific features; there is no cure. It is important to maintain joint positioning and mobility as much as possible using physiotherapy and surgery to correct club feet to allow walking. Ideally, this should be performed by a surgeon with experience of other children with DTD.
Monitoring of abnormalities of the bones of the limbs and, particularly of the spine, is important since surgical treatment may be needed to correct problems. Progressive abnormality of the bones of the spine in the neck is an important complication and should be looked for specifically. This may also require surgical treatment. Surgery to release joint contracture is not usually recommended since these tend to recur.
A range of support for families is available. Sometimes psychological and practical support is needed by somebody affected by DTD to deal with their short stature. Families can obtain information about aids to help with difficulties in access and operation of equipment from local and national statutory and support organisations.
DTD is inherited in autosomal recessive manner. Affected families should be referred to a genetics centre for information and support.
Where DTD is known in a family and the mutations in the SLC26A2 gene are known, chorionic villus sampling can be used at about 10 to 12 weeks or amniocentesis at about 15 to 18 weeks. Ultrasound examination may identify some abnormalities of the skeleton.
Information and support in the UK for diastrophic dysplasia is provided by the Restricted Growth Association (see entry Restricted Growth).