Histidinaemia in Sweden. Report on a neonatal screening programme.

Histidinaemia screening was included in the epidemiological survey of the Swedish neonatal screening programme, 1971-72. Dried blood samples on filter paper collected neonatally from 171,000 infants were analysed the Guthrie method. A blood histidine level above 0.96 mmol/1 (15 mg per 100 ml) was regarded as a positive test and was found in 639 infants - i.e., 1/270. No further diagnostic measures were taken until 1977 when stored dried blood samples from 273 infants with a positive screening test were analysed for urocanic acid. Four children had undetectable blood urocanic acid. They were studied and histidinaemia was confirmed in two children, and excluded in two. Both histidinaemia children had normal psychomotor development at 7 years of age, in spite of the fact that no dietary treatment was given. The incidence of histidinaemia in Sweden was estimated as 1/37,00, on the basis of neonatal screening. In addition, histidinaemia was diagnosed in four individuals who were not detected in the neonatal screening programme; of these, only one had an IQ less than 85. At present, general neonatal screening histidinaemia in Sweden does not seem justified.