Lead poisoning as a toxogenetic disease.

In two non-related patients suffering from acute lead intoxication a persistent decrease in red cell delta-aminolevulinic acid dehydratase (synonym: porphobilinogen synthase) activity of 30%-60% of controls was noted after treatment and normalisation of lead levels and heme precursors in urine and blood. An inherited enzyme deficiency was suggested and confirmed by a subnormal activity in the mothers of both patients. These four persons are considered as heterozygotes with an increased sensitivity to lead exposure.