
histidinemia
a review of published reports of
histidinemia indicates that this condition
has a variability of clinical and biochemical
expression.  three children with histidinemia,
born of a consanguineous marriage
are reported here.  they had blond hair,
blue eyes, speech defects, mental retardation,
and a peculiar eeg abnormality.  they
also exhibited characteristic biochemical
findings of the disease: elevated blood and
urine histidine, increased urine imidazolepyruvic
acid, and a sustained high rise in
plasma histidine following an oral histidine
tolerance test.  they did not, however, have
the reduction of skin histidine a-deaminase
activity which has been observed in some
children with this condition.  tests for determination
of heterozygotes in the family
were not successful.
parental consanguinity and normal skin
a-deaminase activity set these children apart
from other reported cases.  the first lends
support to the hypothesis that histidinemia
is inherited as an autosomal recessive trait;
the second supports the idea that the genic
fault which results in reduced histidine a-
deaminase activity can be expressed to a
different degree in different tissues.  these
children seem to represent a variant of
histidinemia where liver histidase activity is
reduced while skin histidase activity is
present.
