A 19-year-old man presents with severe muscle cramps and early fatigue during sprinting and weightlifting. He reports dark urine after intense exercise. Vital signs at rest are normal (BP 120/80, HR 72, RR 16). Physical examination is unremarkable. Serum creatine kinase is elevated at 850 U/L. During forearm ischemic exercise testing, venous lactate fails to rise appropriately despite normal glucose levels. Urine myoglobin is positive. Which enzyme deficiency best explains these findings?
- A)Glucose 6 phosphatase
- B)Acid alpha glucosidase
- C)Pyruvate kinase
- D)Muscle glycogen phosphorylaseGABARITO
- E)Very long chain acyl CoA dehydrogenase
Explicação
This patient has McArdle disease due to muscle glycogen phosphorylase deficiency. Inability to mobilize glycogen in skeletal muscle causes exercise intolerance, painful cramps, and myoglobinuria, and lactate fails to rise during ischemic or forearm exercise. B... Ver explicação completa e trilha adaptativa →