3q13 microdeletion syndrome is a rare chromosomal anomaly syndrome resulting from a partial deletion of the long arm of chromosome 3. Phenotype can be highly variable, but it is primarily characterized by significant developmental delay, postnatal growth above the mean, muscular hypotonia and distinctive facial features (such as broad and prominent forehead, hypertelorism, epicantic folds, anti-mongloid slanted eyes, ptosis, short philtrum, protruding lips with a full lower lip, high arched palate). Abnormal hypoplastic male genitalia and skeletal abnormalities are frequently present.

Any abnormality of the fontanelles (the regions covered by a thick membrane that normally ossify in the first two years of life) or the cranial sutures (the fibrous joints in which the articulating bones or cartilages of the skull are connected by sutural ligaments ).