Borderline normal intelligence in the Smith-Lemli-Opitz (RSH) syndrome.

We report two sibs with the Smith-Lemli-Opitz (RSH) syndrome and intelligence in the borderline normal range. The proposita has all the features of the syndrome; however, her brother shows fewer signs, indicating that considerable variability of expression may exist for this autosomal recessive trait. Nearly all previous cases had severe to profound mental retardation. The incidence of the syndrome in British Columbia is approximately 1/40,000 live births, giving a heterozygote frequency of about 1/100.