RNF216 and cartilage-hair hypoplasia: To date, various SRA1 gene variants, p.Pro20Leu, p.Tyr35Asn, p.Arg126His and p.Ile179Thr, have been identified in homozygosity, compound heterozygosity, heterozygosity or as digenically inherited with PNPLA6, RNF216 and SEMA7A gene variants in patients with CHH [38,46,47].