Mevalonate kinase deficiency (MKD) is a rare autosomal recessive disorder causing 1 of 2 phenotypes, hyperimmunoglobulin D syndrome and
mevalonic aciduria, presenting with recurrent
fever episodes, often starting in infancy, and sometimes evoked by stress or vaccinations. This autoinflammatory disease is caused by mutations encoding the
mevalonate kinase (MVK) gene and is classified in the group of periodic
fever syndromes. There is often a considerable delay in the diagnosis among pediatric patients with recurrent episodes of
fever. We present a case of an 8-week-old girl with
fever of unknown origin and a marked systemic inflammatory response. After excluding
infections, a tentative diagnosis of incomplete
Kawasaki syndrome was made, based on the finding of dilated coronary arteries on cardiac ultrasound and
fever, and she was treated accordingly. However, the episodes of
fever recurred, and alternative diagnoses were considered, which eventually led to the finding of increased excretion of
mevalonic acid in urine. The diagnosis of MKD was confirmed by mutation analysis of the MVK gene. This case shows that the initial presentation of MKD can be indistinguishable from incomplete
Kawasaki syndrome. When
fever recurs in
Kawasaki syndrome, other (auto-)inflammatory diseases must be ruled out to avoid inappropriate diagnostic procedures, ineffective interventions, and
treatment delay.