Mental retardation in a North Swedish isolate.

Twenty-six mentally retarded patients from a North Swedish geographically isolated population were studied. The mentally retarded patients were short with pycnic body type. Neurological and psychiatric stigmata of variating functions and degrees were recorded. Neurogenic hearing defects, impaired vision, pathological EEG, widened subarachnoidal space found in CT, were among these stigmata. In three patients a urinary substance, probably urocanyl-glycine, was found. The erythrocyte uroporphyrinogen-I-synthetase activity was high in four patients. Chromosome analysis showed some abnormalities which, however, were not systematically present. In the near family 23 persons with schizophrenia were found. The relationship between the mental retardation and the schizophrenic psychosis in the present families has not been explained. Further studies are called for to elucidate the genetic and environmental factors responsible for the two conditions.