Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2024;14(2):e2024139 1 Circumscribed Acral Hypokeratosis: Clinical and Dermoscopic Signs of an Evolving Condition Alessandra Petruzzellis1, Eleonora Di Matteo1, Luca Bianchi1, Francesca Lupi2, Ornella De Pita2, Giuseppe Cianchini2 1 Dermatology Unit, Fondazione Policlinico Tor Vergata, Tor Vergata University of Rome, Rome, Italy 2 UOC Clinical Pathology and Autoimmune and Inflammatory Diseases of the Skin. Cristo Re Hospital, Rome, Italy Key words: hypokeratosis, dermoscopy, rare disease Citation: Petruzzellis A, Di Matteo E, Bianchi L, Lupi F, De Pita O, Cianchini G. Circumscribed Acral Hypokeratosis: Clinical and Dermoscopic Signs of an Evolving Condition. Dermatol Pract Concept. 2024;14(2):e2024139. DOI: https://doi.org/10.5826/dpc.1402a139 Accepted: January 10, 2024; Published: April 2024 Copyright: ©2024 Petruzzellis 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: Alessandra Petruzzellis, Dermatology Unit, Fondazione Policlinico Tor Vergata, Tor Vergata University of Rome, Viale Oxford 81, 00133 Rome, Italy. Email: alessandrapetruzzellis.ap@gmail.com Introduction Circumscribed acral hypokeratosis (CAH) is a rare skin con- dition with an unknown cause, with fewer than 100 reported cases to date. Typically found on the thenar and hypothenar eminences of middle-aged females, it manifests as asymptom- atic depressed erythematous patches with well-demarcated borders [1]. There may be one of more lesions, which per- sist for extended periods. While malignant transformation is rare, it has been documented in a few cases. Histologically, the epidermal depression corresponds to a reduction in the cornified layer, and the elevated borders indicate hyperkera- tosis between the lesion and normal skin [2]. Dermoscopically, the central depressed area exhibits an erythematous pattern with dotted vessels and vascular loops, likely due to thinning of the horny layer and dila- tation of dermal capillaries. White dots correspond to the acrosyringium. The peripheral border displays a “stair step” or “geological strata” configuration with skin layer thicken- ing [3]. These distinctive dermoscopic features facilitate the differentiation between circumscribed palmoplantar hypo- keratosis and common differentials such as Bowen disease and porokeratosis of Mibelli [4]. Case Presentation We present 2 cases of CAH and our considerations about the correlation between clinical-dermatoscopic features and the disease activity. A 78-year-old female presented with 2 depressed ery- thematous patches on the thenar eminence, with evident elevated scaling borders and atrophy in the middle. Dermos- copy showed erythema and a vascular pattern characterized by dotted vessels and white loops in the center and geologi- cal strata aspects in the periphery. The patient reported that these lesions had appeared 4 months before and were in- creasing in size (Figure 1, A and B). A 60-year-old female presented with 2 lesions on the hypothenar eminences of both hands, which looked like 2 slightly erythematous atrophic patches with scaly borders. 2 Research Letter | Dermatol Pract Concept. 2024;14(2):e2024139 Dermoscopy showed a uniform erythematous pattern with some telangiectasias and a border without the typical geo- logical strata look. There lesions were reported to have been stable for 2 years (Figure 1, C and D). Conclusions We hypothesize that the different onset date and evolution might be connected to the slightly different aspects of the lesions. The first patient shows 2 evolving lesions with recent onset, presenting a clear elevated border with the geological strata feature and a rich vascular pattern, while the second had a more stable condition and less evident vessels and pe- ripherical borders. Our hypothesis is that these character- istics, in particular the one on the border, are connected to disease activity, showing a more erythematous vascular pat- tern with well elevated borders when the lesions are evolving and increasing, and with a low slightly scaly border without a rich vascular aspect in the quiescent phase. This theory fits perfectly with the timing of disease activity in our patients. Our longstanding lesion findings differ from those re- cently described by Majluf-Cáceres et al., who reported elongated white structures and a fine white pseudonetwork and hypothesized a correlation with increasing collagen pro- liferation and thickening [5]. Further research should be conducted with more clinical cases in order to confirm our hypothesis and to deepen our knowledge of the pathogenesis and the evolution. References 1. Abignano G, Kapadia A, Lettieri G, et al. Use of optical co- herence tomography for the diagnosis of preclinical lesions of circumscribed palmar hypokeratosis.  Clin Exp Dermatol. 2017;42(2):192-195. doi:10.1111/ced.13027 2. F. Urbina, A. Pérez, L. Requena, A. Rütten, Circumscribed Palmar or Plantar Hypokeratosis 10 Years After the First Description: Figure 1. Clinical and dermoscopic aspects of circumscribed palmoplantar hypokeratosis at different stages of evolution. (A) In the first patient, depressed erythematous patches on the thenar eminence, evident ele- vated scaling borders and atrophy in the middle (B), and dermoscop ic features of erythema, dotted vessels, and white loops in the center, and geological strata aspect in the periphery. (C) In the second patient, sightly erythematous atrophic patches with scaly borders on the hypothenar eminence. (D) Dermoscopy showed uniform erythematous pattern, telangiectasia, and borders without a geological strata aspect. Figure 2. Histological sectio ns of the first patient with active dis- ease: reduction of the cornified layer with a ridge of hyperkeratosis between the lesion and the normal skin. Research Letter | Dermatol Pract Concept. 2024;14(2):e2024139 3 What Is Known and the Issues Under Discussion, Actas Dermo - Sifiliográficas (English Edition), Volume 105, Issue 6, 2014, Pages 574-582, ISSN 1578-2190, https://doi.org/10.1016/j.adengl .2014.05.015. 3. Topin-Ruiz S, Debarre J.-M, Blanchard E, et al. Hypokératose acrale circonscrite (HAC) : utilité diagnostique de la dermosco- pie. Annales de Dermatologie et de Vénéréologie, Volume 144, Issue 3, March 2017, Pages 197-202 4. Dávila-Rodríguez JJ, García L, Posso D, Argenziano G. Der- moscopy of Circumscribed Acral Hypokeratosis.  Dermatol Pract Concept. 2020;11(1):e2020087. Published 2020 Dec 7. doi:10.5826/dpc.1101a87 5. Majluf-Cáceres P, Vera-Kellet C, González-Bombardiere S. New Dermoscopic Keys for Circumscribed Acral Hypokeratosis: Report of Four Cases.  Dermatol Pract Concept. 2021;11(2):e2021010. Published 2021 Mar 8. doi:10.5826/dpc.1102a10