Femoral hypoplasia--unusual facies syndrome and chromosome X trisomy.

A black American infant presented with typical findings of femoral hypoplasia--unusual facies syndrome, chromosome X trisomy in cultured lymphocytes, and a family history of mirognathia among first- and second-degree maternal relatives. It is postulated that micrognathia may lie at one end of the multigenic phenotypic spectrum which at its opposite end includes the above syndrome. The presence of X trisomy in this infant suggests that concordance between this chromosomal anomaly and variable points of the syndrome's phenotypic spectrum should be sought in other families.