Duchenne muscular dystrophy is the most common type of muscular dystrophy. It is an X-linked recessive condition, caused by a mutation to the dystrophin gene. This is the largest gene in the human genome and therefore most vulnerable to mutations.
The dystrophin protein anchors contractile muscle filaments to the sarcolemma of a muscle fibre, allowing the entire cell to shorten during muscle contraction. Mutations to the dystrophin gene result in the expression of a faulty dystrophin protein. As muscle contraction occurs, there is nothing holding the actin filaments to the sarcolemma, causing the sarcolemma to tear. This results in damage to the muscle tissue, eventually leading to muscle atrophy.
The symptoms of the condition generally become noticeable around the age of 5, when parents begin observing their child’s abnormal gait and clumsiness. By the age of 10-12 years of age a child can become wheelchair bound. Continual muscle weakness not only affects the muscles of the limbs, but also those of the heart and chest wall, affecting circulation and breathing, which can prove fatal in the long term.
Having a child affected by muscular dystrophy can be devastating to parents, so it is important to consider the psychological effects on the parents as well as the affected child. Many ethical issues surround genetically inherited conditions and how parents may decide to reduce their risk of having children affected by such a disease through the use of pre-implantation genetic diagnosis.
The flowchart below shows the series of events from the mutated dystrophin gene to the subsequent muscle damage that ensues.