Pathogenic variants of five genes (RSPO4, FZD6, HPGD, PLCD1, and COL7A1) have been reported to cause congenital pure nail disorders, among which FZD6 (frizzled class receptor 6) and RSPO4 are responsible for most of the cases [18,20,33,34]. This evidence concerns the gene RSPO4 and nail disorder.