Definition:

Chromosome 15q24 microdeletion syndrome is a rare microdeletion syndrome characterized by growth retardation, intellectual disability, and distinct facial features including long face with high anterior hairline, hypertelorism, epicanthal folds, downslanting palpebral fissures, sparse and broad medial eyebrows, broad and/or depressed nasal bridge, small mouth, long smooth philtrum, and full lower lip. Other common findings include skeletal and digital abnormalities, genital abnormalities in males, hypotonia, behavior problems, recurrent infections, and eye problems. The recurrent deletions of chromosome 15q24 result from non-allelic homologous recombination (NAHR) mediated by low-copy repeat (LCR, also called segmental duplication) clusters. The deletion occurred as a de novo event in all known cases. Recent study has identified that haploinsufficiency of SIN3A (chromosome 15q24.2) is associated with mild syndromic intellectual disability. This phenotype is highly related to that of individuals with atypical 15q24 microdeletions, linking SIN3A to this microdeletion syndrome.