ACHONDROPLASIA

also called chondrodystrophia fetalis genetic disorder characterized by a lack of cartilage cells. As a consequence, bones that depend on cartilage models for development cannot grow. Achondroplasia is the most common cause of dwarfism. In those afflicted with the disorder, the limbs are very short (fingers reach only to the hips), but the trunk is almost normal in size. The head is enlarged because of some overgrowth of the vault bones following premature closure of sutures at the base of the skull. There is usually a bulging forehead, saddle nose, protruding full-sized jaw, deeply incurved lower back with prominent buttocks, and a narrow chest; women may have narrow pelvises and, subsequently, difficulty in childbirth. The disorder is inherited as an autosomal dominant trait. About 80 percent of cases of achondroplasia result from new genetic mutations, however, rather than from the parental transmission of defective genes. Achondroplastic dwarfs are of normal intelligence and have otherwise normal health. This disorder has been known since antiquity-in Egypt the god Ptah was depicted as an achondroplastic dwarf; in the past, affected individuals were in demand as court jesters and soothsayers.