However, pathogenic variants of the HS6ST1 gene are also common in patients with normosmic/anosmic IHH (approximately 2%), resembling that of KAL1-HH phenotype, but also as an oligogenic cause of CHH together with FGFR1 and NELF genes [36,59,60]. Here, FGFR1 is linked to cartilage-hair hypoplasia.