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[Kurt Hirschhorn, Austrian-born U.S. geneticist, b. 1926; Ulrich Wolf, Ger. geneticist, b. 1933],
A relatively rare disorder caused by a deletion of the short arm of chromosome 4, which results in the absence of a fibroblast growth factor receptor. Its clinical hallmarks include abnormal facial development, delays in attaining neurological and behavioral milestones, mental retardation, short stature, and heart defects. Affected children often succumb to the disease in the first years of life.