[Teratospermia consisting of the absence of the head of the spermatozoa because of a fault in the joint between the head and the neck of the sperm in man (author's transl)].

An ultrastructural sperm study was conducted in a sterile man whose sperm count showed 100 percent headless spermatozoa. Testicular biopsy showed abnormal spermatogenesis : within the spermatid, the sperm head developed separately from the flagellum, which alone was ejected during spermiation.