A case of erythrokeratoderma variabilis: loosened gap junctions in the acanthotic epidermis

A 15-year-old Japanese female without contributory personal or family medical history had demonstrated irregular, keratotic plaques in the lower extremities since infancy that had been gradually enlarging. The keratotic plaques showed partial erythematous change, which altered shape over a relatively short period, leaving pigmentation. The biopsy specimen taken from the erythematous, keratotic plaque showed typical church-spire-like papillomatosis with acanthosis, and thickening of granular and horny layers. Gene analysis targeting connexin 30.3 and 31, based on the diagnosis of erythrokeratoderma variabilis, did not demonstrate any abnormality of these genes. However, ultrastructural observation disclosed an increased amount of gap junctions, some of which showed four layers on high-powered electron microscopy, suggesting loosened connection of the plasma membrane of the keratinocytes through the gap junctions. This loosened gap junction structure was also observed in a case of lamellar ichthyosis, examined as a reference. The disturbed cell-to-cell interaction through latent damage to the gap junctions may be related to the keratotic changes of the epidermis in these skin diseases.