Targeted sequencing in an unselected cohort of CHH patients (n = 334) revealed no rare sequencing variants (RSVs) in FGF21. In contrast, seven heterozygous putative pathogenic RSVs in KLB were identified among 13 CHH probands: p.R309W, p.R309Q, p.R424C, p.A574T, p.F777delF, p.K815E, p.L1011P (Fig EV1A, Table 1). Here, FGF21 is linked to cartilage-hair hypoplasia.