Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2025;15(2):5211 1 Ultraviolet-induced Fluorescence Dermatoscopy Unmasks Dermatoscopically Inconspicuous Terra Firma-Forme Dermatosis and Pityriasis Versicolor Paweł Pietkiewicz1,2, Pille Konno3,4, Natalia Salwowska2,5, Ewelina Mazur2,6,7, Carmen Cantisani8, Aleksandra Lesiak2,9 1 Unitelematica Leonardo Da Vinci, Zug, Switzerland 2 Polish Dermatoscopy Group, Poznań, Poland 3 Dermatology Unit, Confido Medical Centre, Tallinn, Estonia 4 University of Tartu, Tartu, Estonia 5 Department of Dermatology, School of Medicine, Medical University of Silesia, Katowice, Poland 6 Department of Dermatology, Institute of Medical Sciences, Medical College of Rzeszów University, Rzeszów, Poland 7 Doctoral School of the University of Rzeszów, Rzeszów, Poland 8 UOC of Dermatology, Department of Clinical Internal, Anesthesiological and Cardiovascular Sciences, “Sapienza” University of Rome, Rome, Italy 9 Department of Dermatology, Pediatric Dermatology and Dermatological Oncology, Medical University of Łódź, Łódź, Poland Key words: Terra firma-forme dermatosis, Pityriasis versicolor, Ultraviolet radiation, Dermoscopy, imaging, Fluorescence Citation: Pietkiewicz P, Konno P, Salwowska M, Mazur E, Cantisani C, Lesiak A. Ultraviolet-induced Fluorescence Dermatoscopy Unmasks Dermatoscopically Inconspicuous Terra Firma-Forme Dermatosis and Pityriasis Versicolor. Dermatol Pract Concept. 2025;15(2):5211. DOI: https://doi.org/10.5826/dpc.1502a5211 Accepted: July 23, 2023; Published: April 2025 Copyright: ©2025 Pietkiewicz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Paweł Pietkiewicz MD, PhD, Unitelematica Leonardo Da Vinci, 6300 Zug, Switzerland. ORCID ID: 0000-0001- 7262-2456. Email: pietkiewicz.pp@gmail.com Introduction Terra firma-forme dermatosis (TFFD) is an acquired skin condition characterized by poorly defined brown-gray-black patches with a dirt-like appearance [1]. It predominantly affects neck, face, trunk, ankles, and navel of children and young adults [1]. Pityriasis versicolor (PV) is a superficial fungal skin infection usually affecting the trunk of young adults and manifesting as hypo-, normo-, or hyperpigmented macules with a fine scale [2]. Malassezia is the culprit micro- organism, with the scalp serving as an asymptomatic reser- voir of the fungus [1]. Dermatoscopically, TFFD presents as large brown polyg- onal scales or clods, divided by the skin furrows or of linear arrangement, resembling a mosaic pattern [1], whereas PV appears as a depigmented, erythematous, or hyperpigmented 2 Research Letter | Dermatol Pract Concept. 2025;15(2):5211 structureless area featuring a fine scale with a single or dou- ble free edge following the skin markings and perifollicular scaling [2]. Under ultraviolet-induced fluorescence derma- toscopy (UVFD) TFFD displays bright polygonal outlines of the scales [3], whereas PV is characterized by perifollicular greenish fluorescence, light green scaling with an inner free edge and along the skin markings in hypopigmented lesions, or dark structureless area deprived of cutibacterial fluores- cence of porphyrins (blackout areas) in hyperpigmented lesions [2-3]. Case Presentation A 9-year-old boy presented at the dermatology outpatient clinic with tan macules of pityriasis versicolor at the fron- totemporal region that were assessed using dermatoscopy and ultraviolet-induced fluorescence dermatoscopy (UVFD) (DermLite DL5, US). While contact polarized dermatos- copy of the brown plaques of the scalp did not show any characteristic clue to the diagnosis (Figure 1A), UVFD dis- played multiple light greenish roundish folliculocentric scaly areas featuring a scale with a free inner edge (Figure 1B). No other site was affected. During the examination, Woods light inadvertedly directed at the boy’s flank evoked bright fluorescence of otherwise clinically inconspicuous area (Figure 2A-B). Conventional non-contact polarized derma- toscopy did not detect any specific clue to TFFD, whereas a bright rim of polygonal scales typical of TFFD was visualised with UVFD (Figure 2C-D). “Alcohol wipe” test was used to confirm the diagnosis and clearance of TFFD. Direct microscopic examination of the scalp skin scrapings confirmed the presence of “spaghetti and meatballs” appearance of Malassezia. The patient underwent 4-week treatment with 1% ciclopirox olamine shampoo (twice a week). Complete clinical clearance was confirmed at the end of the treatment. Conclusions Here we present an unusual manifestation of two relatively common diseases in a young boy: isolated PV of the scalp and normochromic TFFD of the flank. UVFD is a relatively novel dermatoscopic modality based on the Stokes shift phenome- non that can complement clinical and dermatoscopic exam- ination. In this process, high-energy UV light induces visible light fluorescence of particular chromophores – in our clin- ical scenario, pithyrialactone and keratin, respectively [2-4]. In both conditions UVFD was able to identify specific clues to the diagnosis in clinically and dermatoscopically inconspicuous skin. Figure 1. Isolated pityriasis versicolor (PV) of the scalp in a young boy. (A) Conventional non-contact polarized dermatoscopy shows a few tan structureless areas with no evident dermatoscopic clue to PV (black arrowheads). (B) Ultraviolet-induced fluorescence dermatoscopy reveals multiple light greenish roundish folliculocentric scaly areas featuring typical inward scaling (white arrowheads). Research Letter | Dermatol Pract Concept. 2025;15(2):5211 3 References 1. Sechi A, Patrizi A, Savoia F, Leuzzi M, Guglielmo A, Neri I. Terra firma-forme dermatosis: a systematic review. Int J Der- matol. 2021;60(8):933-943. DOI: 10.1111/ijd.15301. PMID: 33280096 2. Łabędź N, Navarrete-Dechent C, Kubisiak-Rzepczyk H, Bowszyc-Dmochowska M, Pogorzelska-Antkowiak A, Pietkiewicz P. Pityriasis Versicolor-A Narrative Review on the Diagnosis and Management. Life (Basel). 2023;13(10):2097. DOI: 10.3390/life13102097. PMID: 37895478 3. Pietkiewicz P, Navarrete-Dechent C, Togawa Y, et al. Applica- tions of Ultraviolet and Sub-ultraviolet Dermatoscopy in Neo- plastic and Non-neoplastic Dermatoses: A Systematic Review. Dermatol Ther (Heidelb). 2024;14(2):361-390. DOI: 10.1007 /s13555-024-01104-4. PMID: 38358617 4. Pietkiewicz P, Navarrete-Dechent C, Goldust M, Korecka K, Todorovska V, Errichetti E. Differentiating Fordyce Spots from Their Common Simulators Using Ultraviolet-Induced Fluores- cence Dermatoscopy-Retrospective Study. Diagnostics (Basel). 2023 Mar 4;13(5):985. DOI: 10.3390/diagnostics13050985. PMID: 36900129 Figure 2. Terra firma-forme dermatosis (TFFD) in the same young boy inadvertedly detected with Woods lamp. (A) Clinically inconspicuous flank. (B) Examination with Woods lamp uncovers an area of bright fluorescence on a flank (white arrowhead). (C) Conventional non-contact polarized dermatoscopy reveals no characteristic clue to any disease. (D) Ultraviolet-induced fluorescence dermatoscopy produces a bright rim of polygonal scales typical for TFFD (white arrowheads).