Revertant mosaicism (RM) is a phenomenon in which inherited mutations are spontaneously corrected in somatic cells. RM occurs in some congenital skin diseases, although genetic validation of RM in clinically revertant skin has been challenging, especially when homologous recombination (HR) is responsible for RM. We introduced Nanopore Cas9-targeted sequencing (nCATS) for identifying HR in clinically revertant skin. Overall design: Genomic region of COL7A1 which is about 8 kb long was enriched by PCR or nCATS, then applied for MinION sequencing to detect the allele at two loci c.5932C and c.8029G.