Disease name: Becker Muscular Dystrophy, BMD

ICD-10 Disease Code: G71.01 - Duchenne or Becker muscular dystrophy

ICD-10 Disease Group: G71 - Primary disorders of muscles

Becker muscular dystrophy (BMD) is a rare, genetic disorder characterised by progressive muscle weakness in the legs and pelvis due to muscle degeneration. BMD is very similar to Duchenne muscular dystrophy, except the disease progresses at a much slower rate and is less common.

The condition typically begins in childhood, usually after the age of 7, but can also manifest later in life. The slow progressive muscle weakness leads to functional difficulties and may eventually result in wheelchair dependency for about 40% of patients. As the disease advances, it can cause significant respiratory insufficiency due to weakening of the intercostal muscles and diaphragm. Cardiac involvement is also common, often leading to dilated cardiomyopathy, which can occur independently of the severity of skeletal muscle involvement.

BMD is caused by mutations in the DMD gene that encodes the protein dystrophin. Mutations in DMD result in dystrophin deficiency, leading to disease onset.

BMD occurs primarily in males with the occurrence estimated at about 3 to 6 out of every 100,000 births.

In males who inherit the mutated DMD gene, symptoms typically emerge between the ages of 5 and 15 years old, although they can appear later. The primary symptom is progressive muscle weakness, particularly in the lower body, including the legs and pelvic area. This weakness gradually worsens, leading to increased difficulty in walking, often resulting in the need for a wheelchair by ages 25 to 30. Affected individuals may experience frequent falls, difficulty rising from the floor, climbing stairs, and challenges with running, hopping, or jumping. There is often noticeable loss of muscle mass and a characteristic toe-walking gait. Muscle weakness in the arms, neck, and other areas is less severe than in the lower body. Additional symptoms include breathing difficulties, cognitive issues that remain stable over time, fatigue, and loss of balance and coordination. Notably, females rarely develop symptoms.

There is currently no curative treatment for BMD and many of the available treatment options surround symptom management. Management involves a multidisciplinary approach, including physiotherapy to minimise joint contractures and extend the ability to walk, and ankle-foot orthoses for children to prevent Achilles tendon contractures. Cardiac monitoring is crucial, with early treatment of cardiomyopathy using ACE inhibitors or beta-blockers. Cardiac transplantation may be considered for severe cases. Respiratory function monitoring is also important.

Vaccinations against pneumococcal disease and flu are recommended, and respiratory insufficiency is managed with nocturnal BiPAP and cough augmentation.

• https://www.icd10data.com/
• https://www.orpha.net/consor/cgi-bin/index.php
• https://rarediseases.org/
• https://medlineplus.gov/genetics/
• https://www.cdc.gov/

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Becker Muscular Dystrophy (BMD)