Very long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency (MIM 201475) is a rare inherited disorder with three forms of clinical presentation: a severe early-onset form; an intermediate form with childhood onset; and an adult-onset form, of mild severity. During adolescence and adulthood, exercise intolerance, myalgia and recurrent episodes of rhabdomyolysis are the main clinical features. The authors present a case of a 13-year old female, with severe myalgia and dark urine after prolonged exercise. Analytical evaluation showed marked elevation plasma creatine kinase and myoglobin. The increased levels of tetradecenoyl carnitine in patient’s dried blood spot suggested a VLCAD deficiency, which was confirmed by molecular study. Family history is remarkable for first grade consanguinity of parents and a 19-year old brother with records of repeated similar episodes after moderate intensity physical efforts which was subsequently also diagnosed with VLCAD deficiency. This is one of the first cases of late-onset of disease diagnosed in Portugal.

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