To date, 12 genes have been associated with ARCI: TGM1 (MIM 190195), ALOX12B (MIM 603741), ALOXE3 (MIM 607206), ABCA12 (MIM 607800), CYP4F22 (MIM 611495), NIPAL4 (MIM 609383), LIPN (MIM 613924), CERS3 (MIM 615276), PNPLA1 (MIM 612121), CASP14 (MIM 605848), SDR9C7 (MIM 609769), and SULT2B1 (MIM 604125), and at least 10%–15% of affected individuals do not have mutations in any of the known genes (Hellström Pigg et al., 2016; Vahlquist, Fischer, & Törmä, 2018). This evidence concerns the gene PNPLA1 and autosomal recessive congenital ichthyosis.