Through the Lens

Classic porokeratosis of Mibelli Nidhi Singh, Laxmisha Chandrashekar, Nava Kumar, Rakhee Kar1, Devinder Mohan Thappa Departments of Dermatology and 1 Pathology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry ‑ 605 006, India

Access this article online Website: www.idoj.in DOI: 10.4103/2229-5178.146193 Quick Response Code:

Address for correspondence: Dr. Laxmisha Chandrashekar, Department of Dermatology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry 605 006, India. E-mail: laxmishac@ gmail.com

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A 47‑year‑old homemaker presented with recurrent ulcer over left palm and mildly painful fingertip swelling over left thumb and middle finger for past 1 year. She had noticed ring like skin lesion over her left palm since childhood. There was no family history of similar skin lesion. On examination, multiple annular plaques with central atrophy and keratotic ridge at the margin were seen over left side of face, lips, neck, upper back, abdomen, left forearm and left palm. Over the palm, the keratotic ridge ran over thenar and hypothenar eminence, base of fingers, first finger web space and along the thumb and middle finger causing constriction band with bulbous swelling distally at finger tips  [Figure  1]; and nails of the two fingers were dystrophic at the sites adjoining the ridges [Figure 2a‑c]. Annular plaque with keratotic ridge was seen over the left eyelid margins, left side of lower lip involving the mucosal surfaces of lip and lower eyelid and right side buccal mucosa. However, she did not have any discomfort in the oral cavity or eye. There was fissuring at the site of ridge over thenar eminence of left palm [Figure 1]. On dermoscopy, the ridge of the annular plaques was prominently seen along with a thin groove in the keratotic ridge [Figure 2d]. Radiography of the affected hand revealed distal digital narrowing in the left thumb [Figure 2e]. Histopathology from the ridge showed keratin‑filled epidermal invaginations [Figure 3]. There was no evidence of malignancy from the biopsy taken from the fissure or the bulbous projection. Patient was started on acitretin and planned for CO2 laser ablation of the lesions.

DISCUSSION Porokeratosis  (PK) represents a group of disorders of epidermal keratinization characterized by annular lesions with keratotic ridge, which corresponds to cornoid lamella on histopathology.[1] PK was first described and named so by Mibelli in 1893, but still the etiology of PK is unclear. It is

Figure 1: Plaque with central atrophy and threadlike keratotic ridge at the margin over the palm, first finger web space, along the thumb and middle finger causing constriction band with bulbous swelling distally at finger tips

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Figure 2: (a and b) dystrophic nails of the thumb and middle finger with adjoining keratotic ridges, (c) keratotic ridge at adjoining sites of thumb and index finger, (d) its dermoscopic image showing the groove in the keratotic ridge and (e) radiographic image showing distal digital narrowing of the left thumb

common in Caucasians particularly Italians and is rarely observed in dark skinned individuals.[1] The keratotic ridge represents a focal expanding clone of abnormal keratinocytes which could be due to defect in keratinocyte maturation (probably defect in terminal differentiation) or in epidermopoiesis.[2] It has been found to have an autosomal dominant inheritance with variable penetrance. Somatic mutations may explain the sporadic occurrence of cases of PK. In addition, various triggers such as immunosuppression, infection, drugs, ultraviolet

Indian Dermatology Online Journal - 2014 - Volume 5 - Supplement Issue 2

Singh, et al.: Porokeratosis of Mibelli

Malignant transformation has been described in all forms of PK but the risk is highest with linear PK and giant PK.[5] Hence, regular monitoring for malignant transformation should be done, more so if any non‑healing erosion or ulcer is seen in porokeratotic lesion.[1] Dermoscopy helps in better visualization of the keratotic ridge, the classic clinical morphology of PK and should be used as rapid non‑invasive simple clinical diagnostic technique.[6] This case is being presented for the classic morphology of porokeratosis of Mibelli with nail and mucosal involvement.

REFERENCES 1. Figure 3: Keratin-filled epidermal invagination with rising parakeratotic column (H and E ×40) and inset showing higher magnification of keratin filled epidermal invaginations with irregularly arranged keratinocytes with pyknotic nuclei (H and E ×200)

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radiation and mechanical trauma have been incriminated. The clinical variants of PK includes porokeratosis of Mibelli (PM, disseminated superficial porokeratosis, disseminated superficial actinic porokeratosis, porokeratosis palmaris et plantaris (PPP) and PPP disseminata. Nail dystrophy in PK even though rare has been noticed in cases where the lesions involve either the nail matrix or nail bed sometimes finally resulting in complete destruction of nail.[3] Distal digital narrowing associated with nail dystrophy has been reported in a case of linear PK.[4]

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Sertznig P, von Felbert V, Megahed M. Porokeratosis: Present concepts. J Eur Acad Dermatol Venereol 2012;26:404‑12. Shen CS, Tabata K, Matsuki M, Goto T, Yokochi T, Yamanishi K. Premature apoptosis of keratinocytes and the dysregulation of keratinization in porokeratosis. Br J Dermatol 2002;147:498‑502. Kohara Y, Takeo T, Oshima Y, Akita Y, Tamada Y, Watanabe D. Linear porokeratosis with nail dystrophy. Eur J Dermatol 2011;21:625‑6. Tseng SS, Levit EK, Ilarda I, Garzon MC, Grossman ME. Linear porokeratosis with underlying bony abnormalities. Cutis 2002;69:309‑12. Sasson M, Krain AD. Porokeratosis and cutaneous malignancy. A review. Dermatol Surg 1996;22:339‑42. Delfino M, Argenziano G, Nino M. Dermoscopy for the diagnosis of porokeratosis. J Eur Acad Dermatol Venereol 2004;18:194‑5.

Cite this article as: Singh N, Chandrashekar L, Kumar N, Kar R, Thappa DM. Classic porokeratosis of Mibelli. Indian Dermatol Online J 2014;5:130-1. Source of Support: Nil, Conflict of Interest: None declared.

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