The p.(Pro290Ser) variant in PROKR2 gene has been described in CHH patients at heterozygous (Dodé et al., 2006) and homozygous (Sarfati et al., 2010a) states and is always associated with clinical presentations similar to those seen in HH1 (Table 4). The gene discussed is PROKR2; the disease is cartilage-hair hypoplasia.