A 14-year-old male under haematology follow-up for thrombopenia was referred to Neuropaediatrics for presenting an increase in CPK (up to 1864 IU/L), lactate dehydrogenase (LDH) (up to 421 IU/l) and transaminases (aspartate transaminase [AST] up to 490 IU/l, alanine aminotransferase [ALT] up to 280 IU/l) in serial analyses. The patient reported being previously asymptomatic, except for a slight asthenia on moderate exercise, such as running or climbing stairs, occasionally associated with cramps and myalgia. Further anamnesis revealed an isolated episode of macroscopic haematuria following previous exercise. Examination was normal.
An electroencephalogram, electromyogram and muscle magnetic resonance imaging of the lower limbs were performed, with no abnormalities in any of these complementary tests. A muscle biopsy was also performed, which revealed myophosphorylase deficiency, with no other additional alterations. The molecular study revealed the presence of p.R50X (c.148C>T) and p.R490W (c.1468C>T) mutations in compound heterozygosis, confirming the diagnosis of suspected McArdle disease. The patient was referred to nutrition and dietetics, presenting two episodes of rhabdomyolysis prior to dietary coupling that required admission to the paediatric intensive care unit. The patient is currently asymptomatic, with normal CPK values, following nutritional support guidelines and with outpatient controls in Neuropaediatrics and Paediatric Nutrition.
