To the Editor.—In the August issue of the Journal (124:217-221, 1972) Patel et al described two instances of holoprosencephaly. In one of these two cases, the mother was noted to have ocular hypotelorism. This finding suggests that she might represent a forme fruste of the same disorder. To help establish this, without subjecting her to a pneumoencephalogram, the mother's condition might have been evaluated for possible hyposmia.
Careful evaluation of first-degree relatives of holoprosencephalic infants is essential for proper genetic counseling. A dominant form of holoprosencephaly with incomplete penetrance and remarkably variable expressivity is known to occur. Grebe1 described a family in which the propositus had cebocephaly. Other affected individuals with less severe facial dysmorphia, together with anosmia, were observed through five generations with incomplete penetrance. Dallaire et al2 reported familial holoprosencephaly with facial dysmorphia through several generations. Reduced penetrance and marked variation in expression were noted.