A 29 year old male with a history of Crigler–Najjar syndrome and working out with CrossFit, a high intensity core strength and conditioning exercise program, presented with two days of bilateral arm swelling. While he exercised regularly, his recent routine was more rigorous. Initial burning in his deltoids progressed to numbness and swelling. He sought medical care when his urine turned black. His labs were significant for a CK of 99,000, AST to ALT ratio of 1117 to 333, and myoglobinuria. He received aggressive hydration and was ruled out for compartment syndrome. With a negative toxicology screen, he was seen by a neuromuscular specialist who diagnosed him with a presumptive metabolic myopathy, carnitine palmitoyltransferase 2 deficiency.
Carnitine is a hydrophilic quaternary ammonium compound in our body acquired through consumption of meat and dairy products, used by cells in the transport of hydrophobic fatty acids. Three enzyme pathways use carnitine to transport fatty acids from cytosol into the mitochondrial matrix for the production of energy via Beta-oxidation. Carnitine palmitoyltransferase 2 deficiency, the most common inherited disorder of lipid metabolism, prevents this transfer. The age of onset of the first episode varies widely, and patients present with rhabdomyolysis, myoglobinuria, recurrent myalgias and weakness after sustained periods of exercise. The diagnosis is aided by tandem mass spectrometry, enzymatic activity studies in fibroblasts or lymphocytes, low total and free carnitine levels and a high acylcarnitine:free carnitine ratio. Adults often have positive serum or urine myoglobin and serum CK and transaminase levels 20 to 400 times higher than normal levels during an attack. The deficiency has an autosomal recessive pattern of inheritance. Genetic testing is also available. Treatment involves limiting strenuous exercise, restricting lipid intake, avoiding fasting situations, and modifying the diet by replacing long-chain with medium-chain triglycerides supplemented with L-carnitine. Small case series reports support triheptanoin diets and bezafibrate treatment to decrease rhabdomylolsis and improve quality of life. Between attacks, most affected individuals are asymptomatic.
Carnitine palmitoyltransferase 2 deficiency is a very rare disease entity. Our patient was likely misdiagnosed with Criggler-Najjar syndrome as a young boy as his bilirubin has been normal throughout the entire hospitalization. This case raises the importance of thinking about rare genetic entities in young healthy active individuals. As the craze for crossfit increases throughout the country, there may be an increase in the amount of CPT2 deficiency we see uncovered in the adult population.
To cite this abstract:Navetta B, Cohen J. “Crossfit: Not Just Forging Elite Fitness”. Abstract published at Hospital Medicine 2015, March 29-April 1, National Harbor, Md. Abstract 630. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/crossfit-not-just-forging-elite-fitness/. Accessed November 13, 2019.