Genetic recurrent myoglobinuria

Genetic recurrent myoglobinuria is a group of inherited metabolic conditions characterized by repeated episodes of rhabdomyolysis (breakdown of skeletal muscle tissue) leading to the release of myoglobin into the bloodstream and its subsequent excretion in the urine (myoglobinuria). The condition primarily affects skeletal muscle and can secondarily impact the kidneys, as excessive myoglobin can cause acute kidney injury. Episodes are typically triggered by factors such as intense or prolonged exercise, fasting, fever, infections, cold exposure, or certain medications. During an episode, patients may experience severe muscle pain, weakness, swelling, and dark brown or cola-colored urine due to myoglobinuria. Between episodes, patients may be entirely asymptomatic or may have mild exercise intolerance. Genetic recurrent myoglobinuria can result from defects in several metabolic pathways, including disorders of fatty acid oxidation (such as carnitine palmitoyltransferase II deficiency and very long-chain acyl-CoA dehydrogenase deficiency), glycogen storage disorders (such as McArdle disease or phosphofructokinase deficiency), and mitochondrial respiratory chain defects. Because multiple genetic etiologies exist, the inheritance pattern varies and may be autosomal recessive (most commonly), autosomal dominant, X-linked, or mitochondrial depending on the specific underlying gene defect. Age of onset is also variable, ranging from infancy to adulthood. Treatment is primarily preventive and supportive. Patients are advised to avoid known triggers, maintain adequate hydration, and follow dietary modifications tailored to the specific metabolic defect (for example, a high-carbohydrate diet for fatty acid oxidation defects or avoidance of intense anaerobic exercise in glycogenoses). During acute episodes, aggressive intravenous hydration is critical to prevent acute kidney injury. Genetic counseling is recommended for affected families, and identification of the specific underlying genetic defect through metabolic testing and molecular genetic analysis is important for guiding management and prognosis.

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