Phenotypic features in a boy with monosomy 18 mosaicism.

We report on a patient with mosaicism for monosomy 18, a chromosomal abnormality that has been reported only once previously. The patient had cleft lip and palate and mild behavioral and academic problems. His phenotype was milder in comparison with the previously reported patient by Khalifa et al. [1996: Clin Genet 49:318-320]. Further case reports of this chromosomal anomaly will be needed to determine a consistent phenotypic pattern to assist in management and genetic counseling.