Rhabdomyolysis’ Etiology: A Challenging Diagnosis For A General Pediatrician

Background: Rhabdomyolysis is a muscular necrosis with release of its constituents into the circulation. It can be a manifestation of multiple disorders of different origins. A thorough clinical history and laboratorial investigation, with a high index of suspicion are of paramount importance to an accurate diagnosis.

Case: A 6 year old female was admitted to the emergency department (ED) with fever and odynophagia. She had a previous history of intermittent toe-walking and creatine kinase (CK) elevation. A blood test in the ED revealed mild anemia, elevated CK, and serology compatible with Epstein-Barr Virus (EBV) infection. During follow-up, a past history of myalgia and exercise intolerance was found. The patient also presented gastrocnemius hypertrophy, negative Gowers sign and an otherwise normal neurological examination. Continued elevation of CK was detected, so she did baseline metabolic studies and Pompe disease screening with no alterations. A muscle biopsy revealed glycogen deposits and an absence of myofosforilasis, suggestive of McArdle disease, confirmed by the presence of c.148C>T (p.Arg50*) and c.40delA (p.Ile14Serfs*12) variants in PYGM gene. Patient was started on a carbohydrate enriched diet and light to moderate aerobic exercise regimen, and information on rhabdomyolysis was given. A progressive normalization of CK levels and physical activity were observed.

Conclusion: McArdle disease, or type V glycogen storage disease is a rare, recessive autossomic pathology caused by a mutation on the PYGM gene, resulting in a myofosforilasis deficiency. Only 4% of the cases are diagnosed before the age of 10. Its clinical presentation and severity is highly variable, ranging from severe hypotony, gait abnormalities, exercise intolerance, myalgia and muscle fatigue. Patients usually present with elevated CK levels and episodic rhabdomyolysis, myoglobinuria and acute renal failure. This case highlights the importance of investigating rhabdomyolysis’ possible etiologies, in order to prevent or allow an early detection of acute decompensations.