Medical Genetics Abnormalities of chromosome 22q(eg, deletion or monosomy)can be identified in 90% of cases there seems to be an interruption of normal development of pharyngeal pouch structures near the 8th wk of gestation.Medical Genetics Abnormalities of chromosome 22q (eg, deletion or monosomy) can be identified in 90% of cases. There seems to be an interruption of normal development of pharyngeal pouch structures near the 8th wk of gestation