HISTIDINEMIA - A BENIGN METABOLIC DISORDER

Histidinaemia is a relatively common inherited metabolic disorder with an incidence similar to phenylketonuria. This paper reports the long term outcome of patients diagnosed by newborn screening in the north w est of England. Between 1966 and 1990, 108 infants were diagnosed as h aving histidinaemia by a regional neonatal screening programme (incide nce 1:11083). A further five children were detected following diagnosi s in a sibling. Of the 113, nine were lost to follow up. Infants diagn osed before 1981 (n=47) were placed on a low histidine diet (225 mg/kg /d) for an average period of 21 months (SD 4.5). All patients were rev iewed regularly, Griffiths developmental quotients (DQ) were assessed at 2 and 4 years, and WISC-R intelligence quotients (IQ) at 8, 12, and 18 years. IQ data were converted to standard deviation scores (IQ SDS ) to account for increasing IQ norms with time. Neither DQ nor IQ corr elated with plasma histidine at diagnosis or with the mean plasma hist idine throughout life. Growth was normal in all patients. There was no apparent benefit from a low histidine diet in early childhood. In con trast to other studies, there was no excess of clinical symptoms. On t he basis of these findings, histidinaemia is a benign metabolic disord er that does not require treatment.