A 46,XY/46,XY,del(20)(ql3-+ql3.33) mosaicism was identified in a 68 year old man who had mild mental retardation and severe malformation of the limbs. The clinical findings of the patient are compared to those of the very few cases of 20q deletion published to date. (J Med Genet 1993;30:171-3) Constitutional anomalies of chromosome 20 are rare. A few cases have been reported with ring 20,' a few with complete or partial trisomy (mostly of the short arm),2 and a very few with partial deletion of the short or the long arm.3-Deletions of the long arm in particular are extremely rare.We report here an additional case of partial 20q deletion (mosaic) in a malformed man.Case report A 68 year old malformed male, of Jewish Iranian origin, was admitted to hospital after a.,1 .F road accident. He was known to be mildly mentally retarded from childhood. He had married a cousin and fathered four normal children. His wife had no record of abortions or abnormal births.On physical examination the patient had an asymmetrical face, pterygium of both eyes, a low set, malformed left ear, a prominent nasal bridge, prognathism, a short neck, and a flat occiput. Diffuse hirsutism and upper and lower limb malformations were noted. The hands were in an abducted position. On the right hand, the second and fourth digits overlapped the third, and the thumb bones were hypoplastic. On the left hand, congenital absence of the thumb was noted.X rays of the limbs showed dislocation of the radioulnar joint, deformity of the distal radius, and hypoplasia of the scaphoid and metacarpal bones of the thumb in the right arm. In the left arm, dislocation of the wrist, hypoplastic proximal radius, absence of the distal radius, and congenital absence of the thumb were noted. The right leg was normal, whereas the left one had pes cavus with toe clawing and coxa vara (figs 1 and 2).The right leg, injured in the accident, was swollen and showed a giant haematoma. During hospitalisation, lymphoedema developed in this leg. Among other studies, CT scan of both legs was performed, and showed lymphoedema secondary to the injury in the right leg. In the left leg, muscular atrophy was noted, subcutaneous and intramuscular adipose tissue replacing muscular tissue. No abnormalities were noted on neurological examination.A holosystolic murmur was heard over the cardiac apex. Electrocardiogram showed ischaemic changes in the lateral wall, but no symptoms of cardiac disease were present. Echo Doppler studies of the heart showed mild r I: Figure 1 Malformations of the patient's head and limbs.