HSD17B3 and disorder of sexual differentiation: Deficiency of the 17β-hydroxysteroid dehydrogenase type 3 (17 β-HSD3) is a rare autosomal recessive 46,XY Difference of sex development (DSD), resulting from pathogenetic variants in the HSD17B3 gene, which lead to absent or reduced ability to convert Δ4-androstenedione to testosterone in the fetal testes.