Which one of the following is the most likely cause of this presentation?


#1

A 24-year-old man presents complaining of passing red urine. This has also occurred on four to six occasions over the previous few years. The current episode occurred after a game of football and was associated with weakness and cramping of his thigh muscles. His blood pressure is 120n6 mmHg and he has no oedema or muscle tenderness. Urinalysis shows 3+ blood, his plasma creatinine concentration is 146 ~mol/1 and his creatine kinase is 62,652 IU/1. Which one of the following is the most likely cause of this presentation?

A.Camitine palm1ioyltransferase deficiency
B lgA nephropathy
C Muscle trauma with myoglobin-induced tubular injury
D Postinfectious glomerulonephritis
E Renal-cell carcinoma

Explanation
Metabolic myopathy
Aetiology and history
• Carnitine palmitoyltransferase (CPT) deficiency is the commonest cause of inherited metabolic myopathy resulting
in recurrent myoglobinuria Although the metabolic myopathies represent a small
percentage of those presenting with rhabdomyolysis, they should be suspected when myoglobinuria IS recurrent, associated with exercise or fasting and occurring with muscle
cramps or weakness On close questioning. a family history is often present
In a series of 77 cases of ‘idiopathic’ myoglobinuria, a specific muscle enzyme abnormality was identified in 36 ( 47%)
Pathogenesis
• It is likely that, in exercising muscle, ATP and creatine
phosphate become depleted and the maintenance of myocyte
integrity is compromised