Protean cutaneous manifestation caused by <i>ABCA12</i> variants: erythrokeratodermia variabilis-like ichthyosis and unique palmoplantar keratoderma

ABCA12 is crucial for skin barrier function and is traditionally linked to severe congenital ichthyoses, such as harlequin ichthyosis. However, its genotype-phenotype relationship may be more nuanced. Using whole-exome sequencing and Sanger sequencing, we identified four cases of mild ichthyosis with biallelic ABCA12 pathogenic variants. In addition to a milder phenotype, the palmoplantar keratoderma (PPK) in these cases had a distinct 'mosaic tile-like' pattern. Two cases with missense variants in the N-terminus of ABCA12 also presented an annular ichthyosis pattern resembling erythrokeratodermia variabilis et progressiva. Our findings suggest a correlation between ABCA12 missense variant location and clinical presentation, expanding the phenotypic spectrum associated with ABCA12 variants and highlighting the potential for annular patterns or 'mosaic tile-like' PPK in these patients.