Multiple minute digitate hyperkeratosis: A proposed algorithm for the digitate keratoses

Background: Multiple minute digitate hyperkeratosis (MMDH) is a rare disorder of keratinization with many different names. Objective: We present a case of MMDH and review the literature. We propose and discuss the classification the digitate keratoses, which include MMDH, lichen spinulosus, phrynoderma, spiny keratoderma, arsenical keratosis, multiple filiform verrucae, postirradiation digitate keratosis, trichodysplasia spinulosa, and hyperkeratotic spicules. We present a table of suggested and synonymous terms and propose a diagnostic algorithm for these digitate keratoses. Methods: A literature search using PubMed and MEDLINE was performed. This included the search terms "MMDH," "familial disseminated filiform hyperkeratosis," "punctate porokeratotic keratoderma," "disseminated spiked keratosis," "minute aggregate keratosis," "digitate keratosis," "conical keratosis," "hyperkeratotic spicules," and "music box spine dermatosis." A case of MMDH in an 89-year-old woman is described. Results: The digitate keratoses are presented alongside their synonymous terms and are divided into those that are generalized or localized using an algorithm. Limitations: Separate disease entities are likely to arise within the digitate keratoses with increased reporting of immunohistochemical keratin analysis and molecular genetic studies. Conclusion: We report a new case of MMDH and provide a clinical approach to diagnosis of the digitate keratoses.