a chromosomal disorder involving deletion of the short arm of chromosome 5 and characterized by intellectual disability and developmental delays, walking and talking difficulty or inability, and an anomaly of the epiglottis and larynx that causes in infants a high-pitched wailing cry like that of a cat. Almost all affected individuals have very small heads (see microcephaly). The disorder is hereditary in only 10% of cases and more often results from a random event during early fetal development. Also called cat-cry syndrome; chromosome 5, deletion of short arm; crying-cat syndrome; Lejeune syndrome; monosomy 5p.