Recessive mosaicism in ABCA12 causes a unique phenotype of segmental congenital ichthyosiform erythroderma mimicking erythrokeratodermia variabilis.

We report a unique case of a 1-year-old boy presenting with nonpruritic erythematous patches and mild keratotic plaques, partially following the lines of Blaschko and mainly involving the extremities. Next-generation sequencing (NGS) revealed a heterozygous missense mutation c.4724C>T (p.Thr1575Met) and a de novo mosaic deletion mutation c.6861_6869del (p.Leu2288_Gly2290del) in the ABCA12 (NM_173076.3) gene from the DNA of the patient's blood. Even more to the point, the lesional skin showed clinical improvement after 2 weeks of moisturizing treatment. Therefore, partial encapsulation treatment, widely used to enhance the percutaneous absorption of drugs, is suitable for mosaic ichthyosis given its localized skin lesions.