A 17-year-old boy presents with slowly progressive proximal muscle weakness and bilateral calf hypertrophy over 5 years. Vital signs: BP 118/76, HR 88, RR 16, Temp 37°C, SpO2 98%. He remains ambulatory without assistive devices. Serum creatine kinase is 3,200 U/L. His cousin with an identical clinical presentation lost ambulation by age 6. Notably, cardiac examination reveals no murmurs, and echocardiography shows normal ventricular function. Which genetic mutation best explains this milder disease course in this patient?
- A)Loss of upper and lower motor neurons
- B)Autoimmune destruction of motor end plates
- C)Complete absence of dystrophin from a frameshift mutation
- D)Partially functional dystrophin from a nonframeshift mutationGABARITO
- E)Triplet repeat expansion affecting a chloride channel
Explicação
Partially functional dystrophin from a nonframeshift mutation is the correct answer because Becker muscular dystrophy is a milder dystrophinopathy than Duchenne, with later onset and slower progression due to preserved but abnormal dystrophin. Ver explicação completa e trilha adaptativa →