Haptoglobin phenotype frequencies in mentally retarded persons.

Haptoglobin phenotype frequencies for 887 unselected mentally retarded patients were within the range reported for normal European populations. Of these sera, 2% initially classified as anhaptoglobinemic by subjective appraisal of starch-gel electropherograms were subsequently shown to be hypohaptoglobinemic. This frequency of hypohaptoglobinemia is similar to that reported for normal populations. Sixteen of the hypohaptoglobinemic cases were reinvestigated, and all but one showed some evidence of hepatic dysfunction.