Visualization of keratin with diffuse reflectance and autofluorescence imaging and nonlinear optical microscopy in a rare keratinopathic ichthyosis

Funding Information: Funding: This work was supported by grants from the National Research, Development and Innovation Office of Hungary—NKFIH (FK_131916, 2019 (Semmelweis University, M.M.)), EFOP-3.6.3-VEKOP-16-2017-00009 (P.A., S.B.); the New National Excellence Program of the Ministry for Innovation and Technology (ÚNKP-20-4-II-SE-7 (N.K.), ÚNKP-19-3-I-SE-78 (L.F.)); and the European Regional Development Fund project “Time-resolved autofluorescence methodology for noninvasive skin cancer diagnostics” (no. 1.1.1.2/16/I/001, agreement no. 1.1.1.2/VIAA/1/16/014 (I.L., A.L., M.L.)). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Keratins are one of the main fluorophores of the skin. Keratinization disorders can lead to alterations in the optical properties of the skin. We set out to investigate a rare form of keratinopathic ichthyosis caused by KRT1 mutation with two different optical imaging methods. We used a newly developed light emitting diode (LED) based device to analyze autofluorescence signal at 405 nm excitation and diffuse reflectance at 526 nm in vivo. Mean autofluorescence intensity of the hyperkeratotic palmar skin was markedly higher in comparison to the healthy control (162.35 vs. 51.14). To further assess the skin status, we examined samples from affected skin areas ex vivo by nonlinear optical microscopy. Two-photon excited fluorescence and second-harmonic generation can visualize epidermal keratin and dermal collagen, respectively. We were able to visualize the structure of the epidermis and other skin changes caused by abnormal keratin formation. Taken together, we were able to show that such imaging modalities are useful for the diagnosis and follow-up of keratinopathic diseases.publishersversionPeer reviewe