MOSAICISM FOR DEL(17)(P11.2P11.2) UNDERLYING THE SMITH-MAGENIS SYNDROME

Smith-Magenis syndrome (SMS) is a multiple congenital anomalies/mental retardation syndrome associated with deletion of band p11.2 of chromo some 17. The deletion is typically detected by high-resolution cytogen etic analysis of chromosomes hom peripheral lymphocytes. Fluorescence in situ hybridization (FISH) has been previously used to rule out appa rent mosaicism for del(17)(p11.2p11.2) indicated by routine cytogeneti cs. We now report mosaicism for del(17)(p11.2p11.2) in a child with SM S. The mosaicism had gone undetected during previous routine cytogenet ic analysis. FISH analysis of peripheral lymphocytes as well as immort alized lymphoblasts using markers hom 17p11.2 revealed that approximat ely 60% of cells carried the deletion. To our knowledge, this is the f irst case of SIMS associated with mosaicism for del(17)(p11.2p11.2). ( C) 1996 Wiley-Liss, Inc.