Clinical Dermatology Review

: 2021  |  Volume : 5  |  Issue : 2  |  Page : 223--225

Intriguing case of porokeratosis of mibelli on gluteal region

Snehal Balvant Lunge1, Vijayalakshmi M Dhorigol2, Anisha P Bindagi1,  
1 Department of Dermatology, JN Medical College, KLE Academy of Higher Education and Research, Belgaum, Karnataka, India
2 Department of Pathology, JN Medical College, KLE Academy of Higher Education and Research, Belgaum, Karnataka, India

Correspondence Address:
Anisha P Bindagi
Department of Dermatology, JN Medical College, KLE Academy of Higher Education and Research, Belgaum, Karnataka


Porokeratosis (PK) is a rare group of heterogeneous disorders of keratinization representing diverse phenotypic expressions of the same genetic defect, which is mainly inherited in an autosomal dominant manner. This report describes the case of a 40-year-old female with PK over the gluteal region. The rarity of this disorder, unusual site of presentation, and involvement of unilateral side of gluteal region, which is unusual in this form of PK, and the occurrence in a female patient motivated to report this case.

How to cite this article:
Lunge SB, Dhorigol VM, Bindagi AP. Intriguing case of porokeratosis of mibelli on gluteal region.Clin Dermatol Rev 2021;5:223-225

How to cite this URL:
Lunge SB, Dhorigol VM, Bindagi AP. Intriguing case of porokeratosis of mibelli on gluteal region. Clin Dermatol Rev [serial online] 2021 [cited 2022 Jan 28 ];5:223-225
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Porokeratosis (PK) was described by Isidor Neuman in 1875, but has eponymically linked with Vittorio Mibelli, who, in 1893, coined the term “porokeratosis.”[1] It is a rare disorder of epidermal keratinization of unknown etiology and unpredictable course. It shows an autosomal dominant pattern of inheritance with variable penetrance. The sporadic occurrence of cases of PK is explained by somatic mutation.

Various triggering factors such as immunosuppression, AIDS, infection, drugs such as thiazide diuretics, hematological malignancy, ultraviolet radiation, and mechanical trauma have been incriminated in causing PK.[1],[2]

Clinically, it presents as a keratotic papule or annular plaque with a thread-like elevated border that expands centrifugally. The keratotic ridge represents a focal expanding clone of abnormal keratinocytes, which is due to a defect in terminal maturation and differentiation of keratinocytes or in epidermopoiesis.[1]

 Case Report

A 40-year-old female attended the dermatology clinic with complaints of an asymptomatic lesion noticed by her spouse over her buttocks for 3 months [Figure 1]. She did not give any history of pus, blood discharge, and increase in the size of the lesion since its appearance. There was no history of irritant application, and no aggravating or relieving factors when asked further.{Figure 1}

On examination, a solitary erythematous scaly plaque measuring 4 cm × 5 cm with elevated margins having thread-like appearance was present over the right side of the gluteal region. No inguinal lymphadenopathy or any evidence of sexually transmitted disease was present. Routine hematological and biochemical tests were normal. VDRL and ELISA for HIV were negative. A differential diagnosis of mycosis fungoides, Bowen's disease, and PK was considered.

Dermoscopy revealed multiple regularly arranged white globules and vascular pattern with white scales.

Skin biopsy from the margins of the plaque revealed keratin-filled invaginations with parakeratotic column. The rest of the epidermis showed spongiosis, hyperkeratosis, and acanthosis, with the dermis showing no changes [Figure 2] and [Figure 3].{Figure 2}{Figure 3}

The patient was started on topical retinoid cream and emollient and responded well for a period of 2 months with a decrease in the size of lesion by 0.5–0.7 cm, but was further lost to follow-up.


PK represents a group of keratinization disorders occurring mainly in males, classified into localized and generalized forms.[1]

The clinical variants of localized PK include porokeratosis of Mibelli (PM) or classical PK, linear PK, and punctate PK.

Generalized forms include disseminated superficial PK, disseminated superficial actinic PK, porokeratosis palmaris et plantaris (PPP), and PPP disseminate.[1]

PK in a linear arrangement, punctate PK, facial PK, giant PK, genitogluteal reticulate PK, eruptive pruritic papular PK, and ptychotropic PK are the lesser-known forms.[1],[2]

All forms of PK may undergo malignant transformation, with the risk being highest in linear PK and giant PK. Squamous cell carcinoma (SCC) is the most commonly associated tumor, with a few cases of development of Bowen's disease and basal cell carcinoma have also been reported. Hence, regular monitoring of symptoms, size, and morphology has to be done to look out for malignant transformation.

Genitogluteal porokeratosis

PK of the genital area can either be localized or generalized. Involvement of the genital region and adjacent areas (buttocks, perineum, groin, and proximal thighs) may occur as part of generalized PK, occurring elsewhere on the body. PK localized to the genitogluteal region is rare. There are not more than fifty reports in the literature and surprisingly, all the cases are males.

PK is two to three times more common in males than in females, but GP in females seems even rarer. PK restricted to male and female genitalia has been described as scrotal, penoscrotal, penile, vulval, and genito cruro anal and those restricted to buttocks as gluteal PK , encompassing the umbrella term “genitogluteal porokeratosis (GP).”

All cases described under the term “genitogluteal porokeratosis” may be broadly divided into three groups, namely:

Classical PK restricted to the genital-gluteal regionPtychotropic PK, andPenoscrotal PK.

Clinically, they present brownish-to-erythematous keratotic papules and annular plaques with an atrophic center and a raised border. They may be asymptomatic or have local itching.[2] It is important to note that ptychotropic PK arises as a pruritic lesion in the gluteal cleft and is often confused for other inflammatory dermatoses.[2]

The differential diagnosis of GP includes psoriasis, eczema, granuloma annulare, condyloma acuminatum, condyloma latum, Bowen's disease, SCC, extramammary Paget disease, and melanoma, which can be ruled out by histopathological examination.[2]

Dermoscopy of GP shows homogeneous skin-colored to pale area with brown-colored globules and dots, red-brown dots, and different patterns of vessel, along with irregular double-marginated track-like border.

Diagnostic confirmation is achieved through histopathological finding of the cornoid lamella, which is a column of parakeratosis that often bends inward toward the center of the lesion with the absence of the granular layer at its base, which is a characteristic histopathological finding primordial for diagnosis.[3] Of great significance diagnostically are few dyskeratotic keratinocytes just beneath the upper spinous zone. They also arise from adnexal structures, both follicular infundibula and eccrine ostia, as in porokeratotic adnexal ostial nevi.[2],[3],[4]

It is of utmost importance to differentiate between PM and ptychotropic PK because the response of ptychotropic PK to treatment is disappointing and poor. They can be differentiated histologically by the presence of multiple cornoid lamellae, which are present in Ptychotropica PK, and single cornoid lamellae, which are present in the classical PM.[1],[2],[4],[5]

Treatment for PK and GP should be individualized keeping in mind patient's esthetic preference and functionality and the potential to turn malignant. Surgery is the elective treatment, depending on the number and size of the lesions. Other possible approaches include cryotherapy (liquid nitrogen), CO2 laser, dermabrasion, oral and topical retinoids, topical Vitamin D3 analogs, keratolytic agents, topical and intralesional corticoids, topical 5 fluorouracil and most recently 5% imiquimod, 3% topical sodium diclofenac, and photodynamic therapy.[1],[2],[6],[7]


PK restricted to the genitogluteal region is an uncommon entity, and all varieties of GP have been described in men. The “cornoid lamella” is the common unifying histologic finding in all cases, and multiple cornoid lamellae is the rule in both ptychotropic and penoscrotal PK, which is of diagnostic value.

The presence of PM in a dark-skinned middle-aged female and the rare involvement of site, that is, unilateral gluteal region, make this case unique.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.


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