We report on a case with developmental delay and dysmorphic craniofacial features, and a novel~15.2 Mb interstitial deletion within 9q21.11q21.32 confirmed with array comparative genomic hybridization (aCGH). A twenty-two month old boy with inability to walk without support, absent speech, and attention deficit and hyperactivity disorder was seen in our clinic. His craniofacial examination revealed relative macrocephaly, facial asymmetry, frontal bossing, sparse medial eyebrows, hypertelorism, broad base to nose, smooth philtrum, large mouth, operated cleft lip and wide spaced teeth. The high resolution binding (HRB) chromosome analysis revealed an interstitial deletion 46,XY,del(9)(q21) confirmed by aCGH revealing; 46,XY,der(9)(pter→q21.11::q21.32→qter).arr9q21.11q21.32(71,069,763-86,333,272)X1dn. Genotype-phenotype correlations of sixteen cases with 9q21 deletion having different breakpoints and variable length revealed common characteristic features including severe developmental delay, epilepsy, neuro-behavioural disorders and facial dysmorphism including hypertelorism, smooth philtrum and thin upper lip. The smallest overlapping deleted region in all defined cases to date including our case comprised four genes. Among these deleted genes as in our case, especially RORB is considered to be a strong candidate for neurological phenotype.

Keywords: 9q21 microdeletion, autism, behavioral problems, developmental delay, intellectual disability, speech disorder