Circumscribed palmo-plantar hypokeratosis: a disease of desquamation? Immunohistological study of five cases and literature review

Background Circumscribed palmoplantar hypokeratosis (CPH) is a recently recognized, rarely reported dermatosis that shows characteristic clinicopathological features; however, its pathogenesis remains unknown. Objective The aim of this study was to get further insight into the pathogenesis of CPH. Methods An immunohistological study was performed on five cases of CPH to investigate the expression of several epidermal proliferation and differentiation proteins, with emphasis on those involved in corneocyte desquamation [including corneodesmosin, kallikrein 5 and lympho-epithelial Kazal type inhibitor (LEKTI)]. Results In three of five cases, a decreased expression of LEKTI, corneodesmosin and filaggrin was found, along with an increased expression of kallikrein 5 and keratin 6. The expression of several other antigens (including involucrin, Ki67, p63, CD138/syndecan I, EGF-R) did not present a consistently different pattern as compared with the unaffected epidermis. Conclusion The immunohistopathologic features of CPH suggest that an altered (accelerated) corneocyte desquamation process could be the main pathological mechanism underlying the development of lesions.