Partial monosomy of chromosome 1p36.3: A distinctive phenotype

We describe a series of five patients with a partial monosomy of 1p36.3 presenting with a similar syndromic appearance. The phenotype of deletion 1p36.3 patients includes abnormal facies, multiple congenital malformations, and mental retardation.The ages of the patients in our series ranged from 3 to 50 years. As the deletion is very small, detection in the present cases relied upon high resolution G-band analyses and was confirmed with FISH in cases 3 and 5. Patients 2 and 3 were diagnosed as adults; thus smaller deletions in 1p36.33 may be associated with longer life expectancy, but include the critical region for the above phenotype. We noted that the dysmorphic features of the patients are more prominent with older age and are difficult to appreciate in infancy. Observation of this specific 1p36 appears as a white, terminal G-band; detection of a small partial deletion or rearrangement may require greater than 550 band level resolution. FISH utilizing a probe to 1pter can facilitate and confirm these analyses.