Variability in a family with an insertion involving 5p

Cri-du-chat syndrome is due to a partial deletion of the short arm of chrom osome 5 and comprises a catlike cry, minor facial anomalies, growth delays, and psychomotor retardation. We identified a family with an insertion invo lving chromosome areas 5p and 16q, Four relatives are balanced carriers and have a normal phenotype, 5 have inherited the insertion in an unbalanced f orm with 2 resulting in partial trisomy of 5p and 3 in partial monosomy of 5p. The 3 individuals show a variable phenotype with respect to mental dela y and some of the findings of cri-du-chat syndrome. The extent of the 5p de letion in this family was determined using previously mapped markers, The d eletion in this family was informative for further refining the phenotypic map for the cri-du-chat syndrome. This family demonstrates the importance o f performing phenotype-genotype correlation studies based on the presence r ather than the absence of abnormalities. (C) 1999 Wiley-Liss, Inc.