Intermittent mahogany urine

Specialty: Nephrology and urology.

• intermittent non-biliary choluria
• recurrent dark urine due to myoglobinuria or paroxysmal hemoglobinuria

Why it occurs

• Recurrent rhabdomyolysis or intermittent exercise myoglobinuria (in patients with metabolic myopathies such as McArdle disease or carnitine palmitoyltransferase deficiency, where moderate exercise induces repetitive muscle lysis)
• Paroxysmal nocturnal hemoglobinuria (intermittent intravascular hemolysis triggered by mild infections, physical stress, or transient lactic acidosis during sleep)
• Glucose-6-phosphate dehydrogenase deficiency (favism, where the ingestion of beans or certain drugs such as sulfonamides or antimalarials causes intermittent hemolytic crises with hemoglobinuria)
• Acute intermittent porphyria (acute attacks of porphyria triggered by alcohol, prolonged fasting or drugs that stain the urine brown/mahogany)

Initial workup

Urinalysis during the acute episode to distinguish free hemoglobin from intact erythrocytes; serial serum CPK (creatine phosphokinase) levels during and between episodes of dark urine; flow cytometry for CD55/CD59 on peripheral blood; enzymatic assay of glucose-6-phosphate dehydrogenase activity; 24-hour urinary porphobilinogen measurement.

Standard management

• Sodium bicarbonate solution in physiological saline — controlled intravenous infusion during crises to induce alkaline diuresis and prevent acute kidney injury
• Strictly avoid known triggers — oxidant drugs in G6PD deficiency, strenuous exercise without carbohydrates in McArdle, alcohol in porphyria
• Eculizumab (if PNH with severe recurrent hemolytic episodes is diagnosed and confirmed).