Histidinaemia. Part II: Impact; a retrospective study.

Forty-two articles published between 1961 and 1977 describing 43 probands and 26 siblings with histidinaemia were used for the retrospective study. Our objective was to describe the apparent impact of the mutation on development and health in human histidinaemia. The findings were similar to those of an earlier survey (Popkin et al., 1974). Most probands (79%) had a disadaptive CNS phenotype (mental retardation, impaired speech, seizures, aberrant behaviour, and/or learning disorder); half the histidinaemic siblings had a similar phenotype. The modal IQ score was 70; age at recognition of symptoms (CNS phenotype) varied from 1 month to 16 y (modal age 2 1/2 y). There was no correlation between blood histidine (reported values) and occurrence of severity of CNS phenotype. Thirty per cent of histidinaemia subjects, for whom the perinatal history was described, had an abnormal experience. Reported cases with the CNS phenotype apparently represent a very small fraction (about 1%) of all subjects with histidinaemia; this implies that the histidinaemia phenotype is not disadaptive in man.