Non‐ketotic hyperglycinaemia in a family with an unusual phenotype

Abstract

A 10-year-old girl, one of three affected sisters, with non-ketotic hyperglycinaemia is described. In contrast to other reported cases, the course of the disorder was comparatively mild in this family. The only clinical signs were mental retardation and abnormalities in the EEG; blood glycine levels were 2–3 times normal. In the propositus, the formation of¹⁴CO₂ from glycine-1-¹⁴C and of FH ₄ ¹⁴ CH₂OH from glycine-2-¹⁴C were impaired, shown by the decreased¹⁴CO₂ content of expired air and diminished labelling of carbon 3 of serine. However, the biochemical defect was no less than that seen in patients with much more severe clinical effects.