The two most common genetic causes of CAH-X are CYP21A1P-TNXA/TNXB chimeras with pseudogene TNXA substitution for TNXB exons 35–44 (CAH-X CH-1) and TNXB exons 40–44 (CAH-X CH-2). The gene discussed is CYP21A1P; the disease is congenital adrenal hyperplasia.