Effects of a fat load and exercise on asymptomatic VLCAD deficiency

Summary The patient was identified via family screening at the age of 3 years when very long‐chain acyl‐CoA dehydrogenase (VLCAD) deficiency was diagnosed in his sister by newborn screening. Enzyme and molecular analyses confirmed VLCAD‐deficiency (VLCADD). Until the age of 8 years no severe illnesses occurred and the patient was completely asymptomatic without a fat‐reduced and fat‐modified diet. On regular follow‐up, creatine kinase (CK) and liver transaminases were always in the normal range. A long‐chain fat load with 1.5 g/kg body weight did not result in clinical symptoms, nor in elevation of CK or liver transaminases. At the age of 8 years, the patient for the first time complained of recurrent muscle pain after exercise. CK concentrations were elevated up to 20 000 U/L during one of these episodes. Medium‐chain fat was supplemented. With a medium‐chain fat‐rich meal directly before exercise, muscle pain after exercise clearly decreased. In asymptomatic mild VLCADD, a fat‐reduced diet may not be necessary, whereas in later infancy and adolescence, strenuous physical exercise may require additional energy from medium‐chain fat.