ENSG00000290788 and classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency: The presence of this pseudogene is clinically significant in humans: partial gene conversion from a pseudogene to a functional gene causes 21-hydroxylase deficiency; furthermore, copy number variation has been observed in the region containing CYP21A and the neighboring C4A in the HLA region of human chromosome 6 [35].