BMPR1B and Primary amenorrhea: Indeed, Demirhan and colleagues identified a homozygous truncating mutation of BMPR1B underlying a Grebe dysplasia-like phenotype with genital anomalies (absent ovaries, hypoplastic uterus, hypergonadotropic hypogonadism and primary amenorrhea) [8]; and we previously reported a homozygous missense mutation (p.Cys53Arg) and a homozygous nonsense mutation (p.Trp219*) of BMPR1B in Grebe dysplasia [9].