(A) Pedigree. The arrow indicates the proband. (B, C) Generalized ichthyosis and irregularly shaped erythematous plaques. (D) His plantar skin was diffusely hyperkeratotic. (E, F) Compared with healthy control skin (E), the patient’s affected epidermis (F) showed hyperkeratosis, parakeratosis, prominent keratohyalin granules, and acanthosis. (G) The proband was heterozygous for a 1-bp insertion mutation, c.545_546insG (p.Gly183ArgfsTer153). (H–L) Gross (H, I), dermoscopic (J), histological (K), and genetic (L) features of the revertant spot on his left leg. Note that no scales were observed on the revertant spot (arrows). (K) The revertant spot showed histological normalization. (L) The frameshift mutation was lost in the revertant epidermis. Scale bars, 100 μm (E, F, and K) and 5 mm (I).