Mucopolysaccharidosis type 4; deficiency of N-acetylgalactosamine-6-amine-6-sulfatase with defective degeneration of keratan sulfate or chondroitin-6-sulfate. Characteristic features include distinctive skeletal abnormalities, hypooplastic odontoid, aortic insufficiency, and normal intelligence. Death usually occurs by 30 years of age. Condition is autosomal recessive.