Dermatology: Practical and Conceptual


Image Letter  |  Dermatol Pract Concept 2020;10(4):2020112 1

Dermatology Practical & Conceptual

Case Presentation 

A 52-year-old man with no past medical history presented 

with an asymptomatic annular atrophic patch on the distal 

portion of the fourth toe of 2 years’ duration (Figure 1B). 

The lesion began as a small keratotic papule that gradually 

enlarged centrifugally. He had received multiple treatments 

including cryotherapy, topical corticosteroids, antifungals, 

and antibiotics without improvement. Dermoscopic examina-

tion revealed a scaly atrophic erythematous central area with 

a sharply demarcated peripheral hyperkeratotic structure 

(Figure 1A). A skin biopsy of the edge of the lesion revealed 

a cornoid lamella with a column of parakeratotic cells extend-

ing from an invagination of the epidermis with absence of 

granular layer (Figure 1C). The clinicopathologic correlation 

was consistent with porokeratosis of Mibelli. 

Porokeratosis of Mibelli
Constanza Riquelme-Mc Loughlin1, Sebastian Podlipnik1,2

1 Department of Dermatology, Hospital Clínic Barcelona, Universitat de Barcelona, Spain

2 Institut d’Investigacions Biomediques August Pi I Sunyer (IDIBAPS), Barcelona, Spain

Key words: porokeratosis, Mibelli, dermoscopy, cornoid lamella 

Citation: Riquelme-Mc Loughlin C, Podlipnik S. Porokeratosis of Mibelli. Dermatol Pract Concept. 2020;10(4):e2020112.  
DOI: https://doi.org/10.5826/dpc.1004a112

Accepted: May 27, 2020; Published: October 26, 2020

Copyright: ©2020 Riquele McLoughlin and Podlipnik. This is an open-access article distributed under the terms of the Creative Commons 
Attribution License (CC-BY-NC-4.0), which permits unrestricted noncommercial use, distribution, and reproduction in any medium, 
provided the original author and source are credited.

Funding: None.

Competing interests: The authors have no conflicts of interest to disclose.

Authorship: All authors have contributed significantly to this publication.

Corresponding author: Sebastian Podlipnik, MD, Department of Dermatology, Hospital Clínic Barcelona, Universitat de Barcelona, 
Villarroel 170, 08036, Barcelona, Spain. Email: spodlipnik@gmail.com 

Figure 1. (A) Polarized dermoscopy 
(DermLite II PROHR; magnification 
×10) reveals a scaly atrophic erythema-
tous central area, with a sharply demar-
cated peripheral hyperkeratotic structure 
(cornoid lamella). (B) Unilateral annular 
patch on the distal portion of the fourth 
toe of the left foot. (C) Punch biopsy of 
the edge of the lesion reveals a cornoid 
lamella with a column of parakeratotic 
cells extending from an invagination of 
the epidermis with absence of granular 
layer; H&E, magnification  ×40.

A B

C



2 Image Letter  |  Dermatol Pract Concept 2020;10(4):2020112

References

1. Sousa Herênio A, de Morais Cavalcanti SM, Rodrigues de França 

E, Marques Maranhão C, Barbosa de Alencar ER. Porokeratosis 

simulating Bowen’s disease on dermoscopy. An Bras Dermatol. 

2016;91(5 supplement 1):119-121. DOI: 10.1590/abd1806-

4841.20164479. PMID: 28300916. 

2. Navarrete-Dechent C, Uribe P, Marghoob A. Ink-enhanced der-

moscopy is a useful tool to differentiate acquired solitary plaque 

porokeratosis from other scaly lesions. J Am Acad Dermatol. 

2019;80(6):e137-138. DOI: 10.1016/j.jaad.2017.11.052. PMID: 

29221722. 

Teaching Point

Porokeratosis can be mistaken with cutaneous squamous cell 

carcinoma in situ [1], tinea corporis, and circumscribed plan-

tar hypokeratosis, among other annular lesions. Dermoscopy 

is a useful tool that improves diagnostic accuracy and allows 

visualization of the cornoid lamella [2].