47,XX,13+ with Snodgrass phenotype II. Are different chromosomes associated with two clinical varieties of D-trisomy?

Snodgrass et al (1966) divided the D trisomy syndrome into two phenotypic categories based on facial appearance. Patients in their first category had facies associated with defects of prosencephalic cleavage. A striking finding was median cleft lip and palate. In addition there was orbital hypotelorism with severe ocular anomalies, hypoplasia or aplasia of the crista galli, of the median philtrum, and of other parts of the ethnoid bone and the nasal septum. According to these authors, this malformation complex is due to the aberrant development of the embryonic median fronto-nasal process. In the second category of Snodgrass et al, the facies did not exhibit the prosencephalic type of defect. These patients closely resemble each other and bear little resemblance to category I patients. They show mild microcephaly and micrognathia. The nose is large, with a broad ridge and bulbous tip. There are redundant skin folds in the mandibular and periorbital regions. The mouth may be large and turned down. There are no severe optic defects; cleft lip and palate are not usually observed. We have had the opportunity to do an autoradiographic study on an infant girl with category II D trisomy (Fig. 1). The extra chromosome in this case appears to be a D1 (Fig. 2).