Asymptomatic type II hyperprolinaemia associated with hyperglycinaemia in three sibs

Three clinically normal sibs were discovered to have type II hyperprolinaemia in a routine serum amino acid screening programme in Sicily. In addition to the basic biochemical features of type II hyperprolinaemia, all 3 children had marked hyperglycinaemia, whereas their parents had both normal blood proline and glycine concentrations. Clinical normality in individuals with hyperprolinaemia may suggest that these two metabolic disorders (types I and II) are benign entities. Furthermore, the absence of clinical abnormality in these sibs, despite the presence of marked hyperprolinaemia and hyperglycinaemia, may suggest that neither of these findings alone causes brain damage. The hyperglycinaemia in these sibs is unexplained and is an unusual if not unique finding in association with hyperprolinaemia.