Acephalic spermatozoa and abnormal development of the head-neck attachment: a human syndrome of genetic origin

A series of 10 young sterile men with acephalic spermatozoa or abnormal hea d-mid-piece attachments is presented. Nine of these patients had 75-100% sp ermatozoa with minute cephalic ends and 0-25% abnormal :head-middle piece a ttachments. Loose heads ranged between 0-35 for each 100 spermatozoa and no rmal forms were rare, Two patients were brothers. On ultrastructural examin ation, the head was generally absent and the middle piece was covered by th e plasma membrane. When present,:heads implanted at abnormal angles on the middle piece. A testicular biopsy showed abnormal spermiogenesis. The impla ntation fossa was absent and the flagellar anlage developed independently f rom the nucleus, resulting in abnormal head-middle piece connections. In on e patient azoospermia was induced with testosterone to attempt to increase the normal sperm clone during the rebound phenomenon, but all newly formed spermatozoa were acephalic. In another patient with high numbers of defecti ve head-mid-piece connections, microinjections of spermatozoa resulted in f our fertilized oocytes, but syngamy and cleavage did not take place, sugges ting an abnormal function of the centrioles. The findings indicate that ace phalic spermatozoa arise in the testis as the result of an abnormal neck de velopment during spermiogenesis. The familial incidence and the typical phe notype strongly suggest a genetic origin of the syndrome.