Genitogluteal Porokeratoses: A Case Series of a Rare Entity

Dear Editor,

Genitogluteal porokeratosis (GGP) represents a rarer form of porokeratosis (PK) with itchy pruritic lesions confined to the perianal and gluteal areas. It particularly affects middle-aged males with the mean age of diagnosis being 39 years. The presentation is often confusing and misdiagnosed as other dermatoses. Three subtypes of GGP have been described- namely porokeratosis ptychotropica (PPT), penoscrotal porokeratosis (PSP), and classical PK of Mibelli.[1] Herein, we present a case series of eight patients with GGP, showcasing different manifestations of a fundamentally identical condition.

A total of eight adult male patients presented to the dermatology department over 2 years with asymptomatic to itchy annular and verrucous plaques on the buttocks and genito-inguinal areas. The disease duration ranged from 6 months to 5 years [Figures 1(a-e), 2(a and b) and 3(a-c)]. Most cases were intensely pruritic except the solitary lesions (cases 6, 7, 8) which were not associated with itching. Two patients had lesions on the buttocks and gluteal cleft, one on the penis and the other five had lesions on the scrotal area. Out of eight cases, four were of PPT, one of PSP, and three of classical porokeratosis of Mibelli. Case 1 also had additional lesions on the face. Dermoscopy was done in six patients where a double free edge with a keratotic rim was seen in 5/6 cases while one case showed non-specific findings. Follicular plugging and structureless areas were the additive findings seen in cases 1 and 2, respectively. Biopsy was done in five cases where characteristic cornoid lamellae were seen with the absence of a granular layer. A complete blood count (CBC) and viral serological markers for all eight patients ruled out underlying immunosuppression. Venereal disease research laboratory (VDRL) test done in six patients where syphilis was suspected, was non-reactive. A potassium hydroxide mount done in one patient (case 3), ruled out superficial dermatophytosis. The patients were started on topical tretinoin 0.05% gel, imiquimod, and/or oral acitretin along with oral antihistamines. In total, 3 cases (cases 2, 4, and 7) responded well with topical retinoid and case 6 responded well with topical imiquimod [Table 1].

Figure 1.

(a): Multiple, hyperpigmented, annular plaques in a “butterfly” pattern on the gluteal cleft. (b): Irregular, double-marginated “white-track” border (yellow arrow) with follicular plugging (red arrow) (Dermlite DL4 dermoscope, 10×). (c): Annular, erythematous, plaque with a hyperkeratotic rim on the left buttock along with multiple, reddish papules on the right buttock. (d): Multiple, well-defined, erythematous, indurated plaques with hyperpigmented borders, present on the inguinal and scrotal skin. (e): A solitary, erythematous, verrucous plaque present on scrotum

Figure 2.

(a): Multiple, annular, verrucous plaques present discretely on the scrotum and ventral aspect of the penis. (b): Histopathology features of margin of lesion showing epidermal hyperplasia with multiple, angulated, parakeratotic mounds (cornoid lamellae) due to invagination of underlying epidermis along with absence of granular layer (H&E, 40x)

Figure 3.

(a): Single, well to ill-defined, annular plaque with raised, whitish border. (b): Histopathology from the margin of lesion showing multiple cornoid lamella alongwith absence of granular layer (H&E, 40x). (c): A solitary, annular plaque with keratotic borders, present on the scrotum

Table 1.

Genitogluteal porokeratosis: A case series

Age/sex	Location	Clinical presentation	Duration	Dermoscopy	Lab findings	Histopathology	Final diagnosis	Response to treatment & follow-up
25/M	Gluteal cleft and buttocks	Hyperpigmented plaques in a butterfly pattern [Figure 1(a)]	5 years	“white-track border” Follicular plugging surrounded by whitish structureless area [Figure 1(b)]	Complete blood count – WNL; human immunodeficiency, hepatitis B and hepatitis C serology: negative	Multiple cornoid lamella	Porokeratosis ptychotropica	Tab. Levocetrizine (5mg) ×1month Fluticasone proprionate 0.05% cream ×15 days Lost to followup
32/M	Gluteal cleft and buttocks	Annular plaques with hyperkeratotic rim [Figure 1(c)]	1.5 years	Keratin rim	CBC (WNL), human immunodeficiency, hepatitis B and hepatitis C serology: negative	-	Porokeratosis ptychotropica	Tretinoin 0.05% gel × 1month Tab.Levocetrizine (5 mg) ×1month
28/M	Scrotum and bilateral intertriginous area	Erythematous, indurated plaques[Figure 1(d)]	1 year	Double-marginated white-track border	KOH mount negative VDRL negative; human immunodeficiency, hepatitis B and hepatitis C serology: negative CBC – mild leukocytosis with decreased haemoglobin (9.8g/dl)	-	Porokeratosis ptychotropica	Tablet acitretin (25) once daily×1month Tablet Levocetrizine (5mg) × 1 month Lost to follow-up
45/M	Scrotum	Single verrucous itchy plaque on scrotum along with 2-3 annular plaque [Figure 1(e)]	1 year	Brownish keratotic rim of the annular plaque. Verucous plaque- non specific findings	CBC (WNL), VDRL : negative; human immunodeficiency, hepatitis B and hepatitis C serology: negative	Multiple cornoid lamella with absence of granular layer	Porokeratosis ptychotropica with porokeratosis of Mibelli	Tretinoin 0.025% gel
30/M	Scrotum and ventral aspect of penis	Annular, verrucous plaques [Figure 2(a)]	2 years		CBC (WNL), HIV, hepatitis B and hepatitis C serology: negative; VDRL negative	Cornoid lamella with absence of granular layer [Figure 2(b)]	Penoscrotal porokeratosis	Tab.Acitretin (25) ×1 month Tab.Levocetrizine (5 mg) ×1month Desonide 0.05% cream × 15 days Lost to followup
20/M	Shaft of penis	Solitary patch with scaly border [Figure 3(a)]	6 months		VDRL negative; human immunodeficiency, hepatitis B and hepatitis C serology: negative, CBC (WNL)	Consistent with classical porokeratosis [Figure 3(b)]	Porokeratosis of Mibelli	Imiquimod cream for 1month
32/M	Scrotum	Solitary, whitish, annular plaque	1 year	Brownish, keratotic rim	VDRL negative; human immunodeficiency, hepatitis B and hepatitis C serology: negative, CBC (decreased haemoglobin -10.2g/dl)	-	Porokeratosis of Mibelli	Tretinoin 0.025% gel 1month
28/Male	Scrotum	Single itchy veruccous plaque [Figure 3(c)]	2 years	Non specific findings	CBC (WNL), VDRL: negative; human immunodeficiency, hepatitis B and hepatitis C serology: negative	Cornoid lamella with absence of granular layer	Porokeratosis of Mibelli	Tablet levocetrizine 5mg with topical tretinoin 0.025%

M - male, WNL - within normal limits, CBC - complete blood count, KOH - potassium hydroxide, VDRL- venereal disease research laboratory, HIV - Human immunodeficiency virus

PPT, identified by Lucker et al.[2] in 1995, occurs in body folds, particularly the buttocks and natal cleft, where friction is a suspected factor. The condition is linked to trauma, amyloid deposits in tissue, and sometimes immunosuppression, such as in HIV patients. A genetic link to the MVK gene has been noted, especially in cases with disseminated superficial actinic porokeratosis.[3] PPT typically presents as intensely itchy, verrucous plaques that expand over years, sometimes extending to the groin, thighs, and genital area. Misdiagnoses include tinea corporis and psoriasis, but dermoscopy revealing sharply demarcated annular lesions with a thick brown border aids in diagnosis. Treatment options like cryotherapy, 5-fluorouracil, and calcipotriol offer limited success, and approximately 30 cases of PPT have been reported, with one case of malignant transformation, underscoring the need for early diagnosis.[4]

PSP, another subset of GGP, was first described by Joshi et al.[5] in 2014. They described 10 cases of genital porokeratosis limited to the penis and scrotum showing multiple cornoid lamellae on histology. Subsequently, they termed this entity as PSP in another report and proposed the diagnostic criteria for the same.[6] Our patient (case 5) was also a young male in his thirties who presented with intensely pruritic multiple lesions over the penile and scrotal region with multiple cornoid lamellae on histology of 2 years duration. The authors have suggested the possibility of a porokeratosis-like reaction pattern secondary to friction and heat as a cause of PSP, but further validation is needed.[5]

Classic PK of Mibelli is the third type of GGP described, and it is commoner than the PPT and PSP variants. It typically presents with an atrophic annular plaque with raised margin and can involve the penis, scrotum, or buttocks. The common differentials include annular lichen planus and annular syphilis, given the morphology and lesional distribution. In our patients (cases 6, 7, 8), the diagnosis was clinched by dermoscopy. A biopsy in one of the patients showed a single cornoid lamella consistent with PK. Pruritus has been described as a feature in some cases of classical genital PK however, all of our patients were asymptomatic. Topical retinoids usually give a good response in solitary cases but recurrence often occurs.[7]

Our series presents the three variants of GGP, a rare condition typically affecting males (all 8 cases in our series), discussing the various differential diagnoses and reasons for delayed diagnoses. Readers should always consider such an entity when dealing with a longstanding annular and/or verrucous plaque over the genital and gluteal area. Dermoscopy often reveals a characteristic double-edged border, thus clinching the diagnosis. For suspicious cases, a biopsy is essential, especially for longstanding, large, or ulcerative lesions, given the premalignant potential. Long-term follow-up is crucial to monitor for any signs of malignant transformation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the forms, the patients have given their consent for 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.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)

There has been no use of artificial intelligence in the preparation of manuscript.

Funding Statement

Nil.