Duchenne dystrophy, observed in boys younger than 5 years, causes the most severe disease. Cardiomyopathy is common in affected children. Patients with mild cases may lead fairly normal lives, but progressive weakness and scoliosis impairing pulmonary function often results in recurrent infections and exacerbation of weakness. Myoglobinuria is indicated by positive urinalysis with few RBCs on microscopic evaluation. Wide QRS Steroid therapy should be withheld until a definitive diagnosis is made, but many tests that are essential for distinguishing among the varied causes of myopathy are out of the scope of the emergency physician.
Management is supportive.
Patients with rhabdomyolysis warrant inpatient and critical care admission to manage potentially life-threatening renal complications and hyperkalemia. In patients with hypokalemic periodic paralysis, IV or oral potassium replacement may be indicated. Swallowing usually is not impaired, and oral supplementation may blunt the acute attack. IV potassium should be given cautiously, if used at all. Attacks will resolve spontaneously within 4-24 hours, and hyperkalemia may result if potassium supplementation has been excessive.