Breakpoint delineation in 5p‐ patients leads to new insights about microcephaly and the typical high‐pitched cry

Background Cri du chat syndrome (CdCS) is a rare syndrome caused by a partial or complete deletion of the short arm of chromosome 5 (5p‐). The main clinical features include a high‐pitched cry, facial asymmetry, microcephaly, round face at birth, epicanthal folds, hypotonia, delayed growth and development. Methods We studied 14 Brazilian patients with CdCS using genomic array in order to better define the 5p breakpoints and recognize copy number variations (CNVs) that contribute to clinical manifestations associated with the syndrome. Results Array confirmed terminal deletions in 13 patients and an interstitial deletion in one patient. It was also possible to map the breakpoints and associate a genomic region of 4.7 Mb to the development of head circumference and cat‐like cry. We also found other CNVs concomitant to the 5p deletion including a 9p duplication, a 17q deletion, and a 22q deletion in three different patients. Conclusion With advancements of molecular cytogenomic methods in the last two decades, it was possible to evidence cryptic alterations and improve the genotype–phenotype correlation. In this work, we describe a new genomic region associated with microcephaly and cat‐like cry and highlight the importance of precise delineation of 5p deletion breakpoints and detection of other CNVs in CdCS patients to improve genotype–phenotype correlation to perform a complete clinical and molecular diagnosis. We studied 14 Brazilian patients with Cri du chat syndrome using arrays and suggest a new genomic region associated with microcephaly and cat‐like cry. Also we highlight the importance of precise delineation of 5p deletion breakpoints for better genotype–phenotype correlation.