The report of a homozygous splice mutation in RSPO1 predicted to result in an in-frame deletion of the first furin-like domain in R-spondin1 (p.Ile32_Ile95del) in a patient with 46,XX ovotesticular DSD (formerly “true hermaphroditism”) has provided further evidence for the critical role of this protein in humans [21]. This evidence concerns the gene FURIN and disorder of sexual differentiation.