What are the symptoms? Features of BMD include: progressive muscle weakness leading to difficulty with physical activities such as standing up from sitting, climbing up steps, running or walking and, usually later, weakness affecting the upper arms and shouldersjoint contractures can arise from the tightening of tendons, especially the Achilles tendonpseudohypertrophy (enlargement without additional strength) of muscles in the calves and elsewherecardiomyopathy (see entry Cardiomyopathies in children)in the later stages of the disease, respiratory muscle weakness may lead to chest infections. There may also be learning and/or behaviour problems in some children, including difficulty in focusing attention, verbal learning and memory. What are the causes? BMD is caused by mutations in the dystrophin gene. Female carriers of BMD are usually healthy. However, a small number of female carriers of the defective gene are ‘manifesting carriers’ (females who experience some of the effects of the disorder). These problems are usually milder than in a male and are likely to develop later in life. Occasionally, a manifesting carrier may have significant muscle weakness. Manifesting carriers may also have heart problems, which appear as shortness of breath or inability to do moderate exercise. The heart problems, if untreated, can be serious. How is it diagnosed? A test will be made for raised levels of creatine kinase (CK) in the blood. Elevated levels of CK are found in the blood of most individuals with BMD from childhood, sometimes from the newborn period. Further tests will be performed to confirm that the muscle weakness arises from destruction of muscle tissue rather than nerve damage. These may include: genetic tests to look for mutation(s) in the dystrophin gene, usually carried out on a blood sampleelectrical tests carried out on a muscle and/or nervemuscle biopsy (examination of tissue in the pathology laboratory). How is it treated? Currently there is no known cure for BMD, so treatment aims to control symptoms and maintain quality of life. Physiotherapy may help to maintain muscle strength and the range of joint movement; orthopaedic devices such as braces and the use of wheelchairs can improve mobility. Surgery may sometimes be helpful if tendon contractures are problematic. Medication may also be prescribed for cardiac problems. Inheritance patterns and prenatal diagnosis Inheritance patternsBMD is inherited as an X-linked recessive trait. The dystrophin gene is located on the X chromosome, which results in mainly males being affected with the condition. Prenatal diagnosisThis is usually possible where it is known that BMD affects the family and where the family’s particular mutation in the dystrophin gene is known. Preimplantation genetic testing (or diagnosis) (PGT or PGD) may also be used by a female carrier to avoid transmitting the condition to her children. Is there support? Information and support in the UK for Becker muscular dystrophy is provided by Muscular Dystrophy UK (see entry Congenital Muscular Dystrophy).