Familial acro-renal syndrome: clinical, histological and ultrastructural findings. A new case of familial acro-renal syndrome is reported. The mother and a female sibling were also affected. The male infant of the third pregnancy born to the patient had typical features of the syndrome. His two healthy sisters and his sister-in-law were not affected. The first pregnancy was interrupted due to fetal hydrops, and the two subsequent pregnancies were also terminated by abortion. Post-mortem examination of the abortuses revealed the development of a complete mesonephric duct in both patients. In the father, the complete duct could not be demonstrated, but only a remnant of the mesonephric duct, together with a small mesonephric remnant, were seen in the epididymis. No anomaly was observed in the fetus from the patient's first pregnancy, as well as in a series of healthy men. The possible relationship of these findings with the observed pathology is discussed. The possible etiology of the syndrome is briefly reviewed, and the results of a family survey are reported.