Major feeding difficulties in the first reported case of interstitial 20q11.22-q12 microdeletion and molecular cytogenetic characterization

We report on a 4-year-old female presenting with intrauterine growth retardation, facial dysmorphic features, major feeding difficulties with severe diarrhea and vomiting, mental retardation with abnormal behavior and hypertonia. Feeding difficulties were the most invalidating features with absent oral intake requiring persistent enteral feeding. Standard cytogenetic studies were normal, but high-resolution chromosome analyses revealed a small de novo interstitial deletion of the long arm of chromosome 20, 46,XX,del(20)(q11.21q12). The deletion was confirmed using metaphase comparative genomic hybridization (CGH) and multicolor high resolution banding (mBAND). The deletion breakpoints were characterized using FISH analyses with YACs, PACs, and BACs clones located in the deleted and adjacent regions. A 6.6-Mb deleted region between markers D20S815 (20q11.22) and D20S435 (20q12) could be delineated. None of the nine previously reported cases with interstitial 20q deletion found in the literature involve the same breakpoints. This report further emphasizes the indication of high-resolution chromosome analyses in children with syndromic mental retardation. The description of additional cases would be useful in order to better characterize the phenotype of patients with proximal interstitial 20q deletion.