A chromosomal anomaly characterized by developmental delay, childhood hypotonia, facial dysmorphism, and friendly/amiable behavior. Abnormal hair pigmentation and texture is also frequent. Short stature, pectus excavatum, spine anomalies, dislocation of the hip, long slender fingers and slender lower limbs, and positional deformities of the hands/feet have also been reported. In all patients, global psychomotor developmental delay is noted from an early age. The recurrent 17q21.31 deletion encompasses at least six genes: C17orf69, CRHR1, IMP5, MAPT, STH and KIAA1267.