We present a case of a nearly 3-year-old girl who was admitted to hospital due to severe hypernatremia (196 mmol/l). Her medical history included central hypothyreosis and growth hormone deficiency. Rehydration and normalization of sodium was achieved according to guidelines. On the fourth day of hospitalization, the patient developed tremor, ataxia, and rigor. Cranial magnetic resonance imaging (cMRI) was performed and (mis)interpreted for meningoencephalitis, with corresponding diagnostic and therapeutic implications. The patient had extrapontine myelinolysis. The child recovered completely after hospitalization for nearly 2 weeks.

A 9-month-old Turkish girl was admitted several times within 3 months to the hospital in reduced general condition and with extreme tachypnea. The patient had been diagnosed with phenylketonuria (PKU) in newborn screening and has been treated with a low phenylalanine diet and amino acid supplements. Each time an unexplained pronounced metabolic acidosis was noted, and the child was treated with sodium-bicarbonate and glucose-electrolyte infusions. The acidosis with only slightly abnormal glucose, normal lactate levels and pronounced ketonuria suggested a defect in ketone body utilization. Succinyl-CoA: 3-oxoacid CoA transferase (SCOT) enzyme activity was low in patient's fibroblasts. Mutation analysis of the corresponding OXCT1 gene revealed that the patient was a homozygous carrier of the mutation c.1523T>C (p.V508A). We conclude that SCOT deficiency should be considered in the differential diagnosis in patients with recurrent metabolic acidotic episodes, even if they are already known to have a metabolic disease unrelated to this.