This is an X-linked recessive disease, the majority of which are caused by large scale deletions within the dystrophin gene (the remaining- 30%- are a mix of point mutations, microdeletions, insertions etc). The dystrophin protein is essential for the stability of cell membranes, and have important interactions with proteins, particularly within muscle cells.
The clinical presentation is quite typical:
- Delay in motor development followed by observable muscle weakness at age 3-4. This mainly affects the proximal hip and shoulder girdles and can be observed as Gower’s sign (patient must use all four limbs to stand from a sitting position). Patients may also try to compensate for proximal weakness by ‘toe-walking’.
- They may show pseudohypertrophied calfs. This is classical of DMD.
Patient’s will usually be wheelchair bound by 12-15 years old and unfortunately will die in their 20s due to respiratory involvement.
Investigations that may be useful include blood tests (high Creatinine Kinase- due to muscle wasting and breakdown); muscle biopsy (stain for dystrophin); genetic tests; EMG.
Corticosteroids may improve symptoms and duration of life but will not change outcomes.