Sertoli Cell-Only Syndrome

Sertoli cell-only syndrome is the most severe form of nonobstructive azoospermia with either no germ cells present in seminiferous tubules (type 1) or germ cells present only in a minority of tubules (type 2). In this syndrome, Sertoli cells are the only cells that line the seminiferous tubules. The patients have normal secondary sexual characteristics and normal or small-sized testes. In 1947, Del Castillo et al. originally reported five infertile men with bilateral small testes, normal phallus, sterility with azoospermia, a testicular biopsy which showed small seminiferous tubules, complete absence of germinal epithelium, presence of Sertoli cells, and normally appearing Leydig cells. They also found normal urinary follicle stimulating hormone (FSH) levels and decreased 17-ketosteroid excretion (Del Castillo et al. 1947). The exact prevalence of Sertoli cell-only syndrome is as yet undetermined; however, it is estimated that less than 5–10% of infertile men may be affected by this syndrome (Ramphul et al. 2019).