Duchenne_Muscular_Dystrophy_Flashcards
What is Duchenne muscular dystrophy?
Duchenne muscular dystrophy is an X-linked recessive disorder affecting dystrophin genes, essential for normal muscle function.
What are the key features of Duchenne muscular dystrophy?
Features include progressive proximal muscle weakness starting around 5 years, calf pseudohypertrophy, Gower’s sign, and intellectual impairment in about 30% of patients.
How is Duchenne muscular dystrophy investigated?
Investigation typically includes measuring raised creatinine kinase levels and genetic testing, which has replaced muscle biopsy for definitive diagnosis.
What is the management approach for Duchenne muscular dystrophy?
Management is largely supportive as there is currently no effective treatment for Duchenne muscular dystrophy.
What is the prognosis for patients with Duchenne muscular dystrophy?
Prognosis includes inability to walk by age 12, survival typically into the 20s or early 30s, and complications such as dilated cardiomyopathy.
summarise
Duchenne muscular dystrophy
Duchenne muscular dystrophy is an X-linked recessive inherited disorder in the dystrophin genes required for normal muscular function.
Features
progressive proximal muscle weakness from 5 years
calf pseudohypertrophy
Gower’s sign: child uses arms to stand up from a squatted position
30% of patients have intellectual impairment
Investigation
raised creatinine kinase
genetic testing has now replaced muscle biopsy as the way to obtain a definitive diagnosis
Management
is largely supportive as unfortunately there is currently no effective treatment
Prognosis
most children cannot walk by the age of 12 years
patients typically survive to around the age of 25-30 years
associated with dilated cardiomyopathy
A four-year-old boy has presented with his concerned mother with an abnormal gait and weakness in his lower limbs. A history, examination and subsequent investigations are completed and he is diagnosed with Duchenne muscular dystrophy.
What is the most common cardiac pathology associated with this condition?
Acute myocardial infarction
Atrioventricular septal defect
Coronary aneurysms
Dilated cardiomyopathy
Tetralogy of Fallot
Dilated cardiomyopathy
The most common heart lesion associated with Duchenne muscular dystrophy is dilated cardiomyopathy
Important for meLess important
Acute myocardial infarctions are not associated with Duchenne muscular dystrophy
Atrioventricular septal defects are not associated with Duchenne muscular dystrophy. However, it is associated with Down syndrome.
Coronary aneurysms are not associated with Duchenne muscular dystrophy. It is a complication of Kawasaki disease, a medium vessel vasculitis affecting children from 6 months to 5 years.
Dilated cardiomyopathy is associated with Duchenne muscular dystrophy and is, therefore, the correct answer. Duchenne muscular dystrophy is an X-linked recessive condition that is characterised by progressive muscle-weakening and wasting. The complication of dilated cardiomyopathy usually begins in adolescence and is rapidly progressive.
Tetralogy of Fallot is a cyanotic cardiac condition that presents at birth. It is not associated with Duchenne muscular dystrophy.
A concerned mother brings her 4-year-old son to see the GP, worried about his walking and balance. The child learned to walk around 2 years old, much the same as his older sister. However, over the last few months, his mum has noticed that he has become reluctant to walk and often trips or falls when he does.
On examination, the child is slim built but has disproportionately large calves. When asked to walk across the room he does so on his tiptoes. Gowers test is positive.
What investigation is considered most appropriate to confirm the likely diagnosis?
CT imaging of legs
Creatine kinase levels
Genetic analysis
Muscle function tests
Proximal muscle biopsy
Duchenne muscular dystrophy: genetic testing rather than a muscle biopsy is now used to make a diagnosis
Important for meLess important
Genetic analysis is correct. The history and presentation outlined are strongly suggestive of a diagnosis of Duchenne muscular dystrophy (DMD), an x-linked recessive genetic disorder that causes wasting and weakness of the muscles. Calf hyperplasia and a positive Gowers test (walking the arms up the legs to get up from the floor) are classical features of DMD. The majority of affected individuals will be wheelchair-bound by puberty, and management is mostly conservative.
CT imaging of the legs is incorrect. This may show evidence of muscle breakdown and fat hyperplasia in the calves. However, it is not typically used in the diagnosis of DMD.
Creatine kinase is incorrect. Creatine kinase is released in the blood when muscles are damaged. A high creatine kinase can be a strong indicator of muscular dystrophy in children. However, genetic testing is more appropriate for obtaining a definitive diagnosis.
Muscle function testing is incorrect. This is often used to monitor the disease progression of DMD, however, it is not used in the initial diagnostic process.
Proximal muscle biopsy is incorrect. Although a biopsy of the affected muscles would also provide the correct diagnosis and has previously been considered the gold standard, genetic analysis is now preferred.
