{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T15:27:34Z","timestamp":1775662054004,"version":"3.50.1"},"reference-count":35,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T00:00:00Z","timestamp":1772236800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"\u201cInnovative Medical Research\u201d fund of the University of M\u00fcnster Medical School","award":["S\u00dc212007"],"award-info":[{"award-number":["S\u00dc212007"]}]},{"name":"German Dermatological Society (\u201cDeutsche Dermatologische Gesellschaft"},{"DOI":"10.13039\/501100006693","name":"Arbeitsgemeinschaft Dermatologische Forschung","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100006693","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Dermatopathology"],"abstract":"<jats:p>Background: Inherited ichthyoses are a heterogeneous group of disorders of cornification caused by mutations in genes encoding epidermal proteins. Clinically, patients with ichthyosis present with erythema, scaling, and occasionally blistering; some subtypes are syndromic. Accurate and timely diagnosis is essential for appropriate management and genetic counseling. Objectives: Diagnosis of ichthyosis typically relies on a combination of clinical features, histopathological and ultrastructural findings, immunohistochemistry, and molecular genetic testing. Dermatopathology can be particularly valuable in three diagnostic scenarios: (i) when the clinical diagnosis of ichthyosis is evident, but the specific subtype remains unclear; (ii) when differential diagnoses such as inflammatory dermatoses need to be excluded; and (iii) when molecular testing is unavailable or yields variants of uncertain significance. However, definitive classification according to current nomenclature requires molecular confirmation. Methods: Despite being a routine diagnostic tool in dermatology, histopathological criteria for ichthyoses remain ill-defined and diagnostically challenging. In this retrospective study, we systematically assessed histological features in 66 patients with confirmed ichthyosis. Results: Our analysis revealed six distinct histological patterns. Based on these, we propose a pattern-based diagnostic algorithm to support the histological classification of ichthyosis subtypes. Limitations: Although some rare subtypes were underrepresented, this cohort represents the largest and most heterogeneous group of molecularly confirmed ichthyosis cases analyzed histologically to date. Conclusions: Our findings highlight the diagnostic value of skin biopsies in inherited ichthyoses. The delineation of characteristic histological patterns and the development of a diagnostic algorithm may facilitate more accurate subtype identification, particularly in settings where genetic testing is limited or inconclusive.<\/jats:p>","DOI":"10.3390\/dermatopathology13010009","type":"journal-article","created":{"date-parts":[[2026,3,5]],"date-time":"2026-03-05T14:19:21Z","timestamp":1772720361000},"page":"9","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Defining Histological Patterns in Inherited Ichthyoses: Toward a Diagnostic Algorithm Based on 66 Confirmed Cases"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7284-9949","authenticated-orcid":false,"given":"Kira","family":"S\u00fc\u00dfmuth","sequence":"first","affiliation":[{"name":"Department of Dermatology and Allergology, Helios Klinikum Berlin-Buch, Campus of Medical School Berlin, 13125 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vinzenz","family":"Oji","sequence":"additional","affiliation":[{"name":"Department of Dermatology, University Hospital of M\u00fcnster (European Reference Network for Rare Skin Diseases (ERN Skin)), 48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jacqueline","family":"Bodes","sequence":"additional","affiliation":[{"name":"Department of Dermatology, University Hospital of M\u00fcnster (European Reference Network for Rare Skin Diseases (ERN Skin)), 48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Isabelle","family":"Jochum","sequence":"additional","affiliation":[{"name":"Department of Dermatology and Allergology, Helios Klinikum Berlin-Buch, Campus of Medical School Berlin, 13125 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Florian","family":"Muhs","sequence":"additional","affiliation":[{"name":"Department of Dermatology, University Hospital of M\u00fcnster (European Reference Network for Rare Skin Diseases (ERN Skin)), 48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6076-9992","authenticated-orcid":false,"given":"Katalin","family":"Komlosi","sequence":"additional","affiliation":[{"name":"Institute of Human Genetics, Medical Center\u2014University of Freiburg, Faculty of Medicine, University of Freiburg (European Reference Network for Rare Skin Diseases (ERN Skin)), 79106 Freiburg, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1095-4962","authenticated-orcid":false,"given":"Ingrid","family":"Hausser","sequence":"additional","affiliation":[{"name":"Institute of Pathology, Heidelberg University Hospital, 69120 Heidelberg, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Matthias","family":"Schmuth","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Venerology an Allergy, Medical University Innsbruck, Karl Landsteiner Institute for Pediatric Dermatology and Rare Diseases (European Reference Network for Rare Skin Diseases (ERN Skin)), 6020 Innsbruck, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Heiko","family":"Traupe","sequence":"additional","affiliation":[{"name":"Department of Dermatology, University Hospital of M\u00fcnster (European Reference Network for Rare Skin Diseases (ERN Skin)), 48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8580-8118","authenticated-orcid":false,"given":"Judith","family":"Fischer","sequence":"additional","affiliation":[{"name":"Institute of Human Genetics, Medical Center\u2014University of Freiburg, Faculty of Medicine, University of Freiburg (European Reference Network for Rare Skin Diseases (ERN Skin)), 79106 Freiburg, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dieter","family":"Metze","sequence":"additional","affiliation":[{"name":"Department of Dermatology, University Hospital of M\u00fcnster (European Reference Network for Rare Skin Diseases (ERN Skin)), 48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1093\/bjd\/ljaf154","article-title":"Nonsyndromic epidermal differentiation disorders: A new classification toward pathogenesis-based therapy","volume":"193","author":"Akiyama","year":"2025","journal-title":"Br. 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