Hyperkeratotic hand eczema (HHE) is a characteristic hand eczema subtype with a mostly unknown pathophysiology.

A study was conducted to examine histopathology, expression of keratins (K), epidermal barrier proteins and adhesion molecules in HHE.

Palmar lesional and perilesional skin biopsies were acquired from seven HHE patients and two healthy controls. Also, 135 candidate genes were screened for mutations that were associated with palmoplantar keratoderma.

Immunofluorescence staining revealed a significant reduction of keratin 9 and keratin 14 in lesional skin. Up-regulation of K5, K6, K16, and K17 was found in lesional skin as compared to perilesional and healthy palmar skin. Moreover, upregulation of involucrin and alternating loricrin staining, in an extracellular staining pattern, was also found. Filaggrin expression was comparable in lesional, perilesional and healthy control skin. There were no monogenetic mutations.

The study concluded that at present, the phenotype of HHE is included in the hand eczema classification system. The manifested expression of filaggrin and involucrin in lesional skin does not give any evidence of pathogenesis of atopic eczema. The upregulation of K6, K16 and K17 and decrease of K9 and K14 can possibly contribute to the underlying pathogenesis.

Source: Klaziena Politiek, Laura Loman, Hendri. H. Pas, et al. Hyperkeratotic hand eczema – eczema or not? First published: Contact Dermatitis. 2020 Apr 25, https://doi.org/10.1111/cod.13572