RTEL1 and hypotrichosis 1: Over the last 20 years, several more genes associated with autosomal dominant and autosomal recessive DC have been discovered, but the only genes with variants also seen in HHS include TERT, DKC1, RTEL1, TNIF2, ACD, and PARN. TNIF2 and ACD encode components of the shelterin complex while RTEL1 encodes a DNA helicase that associates with telomerase and PARN encodes a poly-A-specific 3’ exoribonuclease (Glousker et al. 2015; Bertuch 2016).