an autosomal recessive disorder (see recessive allele) marked by polydactyly (extra fingers or toes); poorly formed hair, teeth, and nails; and dwarfism. Associated abnormalities may include genital anomalies and heart defects. A high incidence of the disorder is seen among the Old Order Amish of Pennsylvania. Also called chondroectodermal dysplasia. [Richard White Bernard Ellis (1902–1966), British physician; Simon van Creveld (1894–1971), Dutch pediatrician]