To test if HMGCS2 plays an important role in gonad development in humans we first used 1 million probe comparative genomic hybridization arrays (aCGH) on genomic DNA from twenty-three unexplained cases of 46,XY GD European descent, for which variants in SRY and in other genes known to cause 46,XY DSD, such as nuclear receptor subfamily 5, group A, member 1 (NR5A1) and mitogen-activated protein kinase kinase kinase 1 (MAP3K1) [6, 54, 55], were excluded. The gene discussed is MAPK1; the disease is disorder of sexual differentiation.