What are the symptoms? MG is characterised by fluctuating weakness that becomes worse with increasing effort. Sometimes it affects only the eye muscles (ocular myasthenia) causing double vision and drooping of the eyelids. More commonly, the condition is generalised with weakness variously affecting not only the eye muscles but also the face, throat, neck, trunk, limbs and muscles that are involved in breathing. Some improvement in strength is achieved by rest. Individuals with LEMS also have weakness of the legs and arms and there may also be disturbance of the autonomic nervous system, which can cause dry mouth and constipation. This type of MG is extremely rare in children. CMS causes variable muscle weakness affecting the eyes, face, trunk, limb, breathing and swallowing muscles, which may be present from birth or develop in early childhood. How is it treated? MG usually responds at least partially to treatment with pyridostigmine by mouth, which prolongs the action of acetylcholine at the nerve-muscle junction and makes the muscles stronger. In more severe cases, treatment with steroids and/or other immunosuppressive medications such as azathioprine may be needed to reduce antibody production and improve muscle strength. In generalised MG with antibodies that attack the acetylcholine receptor, a thymectomy (an operation to remove the thymus gland, which is situated behind the breast bone) may help improve muscle strength. Thymectomy is not helpful in MG with MuSK antibodies, LEMS or CMS. LEMS is treated with 3, 4 diaminopyridine (DAP), which enhances acetylcholine release from nerve endings and/or other immunological treatments (not thymectomy). Some CMS respond well to pyridostigmine and 3,4 DAP. However, some subtypes of the condition are made worse by pyridostigmine, so it is important to have a precise genetic diagnosis before treatment, or for medication to be given for the first time in hospital. Salbutamol (albuterol) or ephedrine may be helpful in these cases. Treatment with quinidine or fluoxetine is used for a subtype of CMS called the slow channel syndromes. Adults and children with MG, LEMS and CMS are at risk of life-threatening swallowing and breathing difficulties, particularly with chest infections and should have fast-track access arranged to their local hospital. Temporary supportive care using a breathing machine and/or tube feeding may be needed to aid recovery. Those with repeated breathing problems should also be under the care of a specialist respiratory centre. Inheritance patterns and prenatal diagnosis Inheritance patternsThere is a very weak familial susceptibility to MG and to other autoimmune diseases in the families of patients with MG and LEMS. However all CMS are genetic disorders, most are autosomal recessive, apart from the slow channel syndromes, which are autosomal dominant. It is important to be referred to your regional genetics centre for further information if a CMS is diagnosed. Prenatal diagnosisThis is not applicable to MG and LEMS. Prenatal diagnosis is now possible for CMS families, once the exact genetic fault is identified. Is there support? Myaware (Myasthenia Gravis Association) Helpline: 01332 290 219Email: firstname.lastname@example.org Website: myaware.org The Association is a Registered Charity in England and Wales No. 1046443. It provides information and support to people affected by Myasthenia Gravis, Congenital Myasthenic Syndrome and Lambert Eaton Myasthenic Syndrome. Myaware Kids provides support for children with myasthenia and their parents and carers via its active Facebook group, and holds an annual weekend get-together. Group details last updated February 2016.