
==== Front
Indian J Dermatol
Indian J Dermatol
IJD
Indian J Dermatol
Indian Journal of Dermatology
0019-5154
1998-3611
Wolters Kluwer - Medknow India

IJD-69-365c
10.4103/ijd.ijd_131_24
E–IJD®: Short Communication
A Clinico-Epidemiological Study on Porokeratosis
Shirahatti Trishala
Bangaru H 1
Sathish S 1
From the Department of Dermatology, St Johns Medical College Hospital, Bengaluru, Karnataka, India
1 Department of Dermatology, Mysore Medical College and Research Institute, Mysore, Karnataka, India
Address for correspondence: Dr. Trishala Shirahatti, Department of Dermatology, St Johns Medical College Hospital, John Nagar, Koramangala, Bengaluru, Karnataka, India. E-mail: trishala.shirahatti@gmail.com
Jul-Aug 2024
19 8 2024
69 4 365365
2 2024
4 2024
Copyright: © 2024 Indian Journal of Dermatology
2024
https://creativecommons.org/licenses/by-nc-sa/4.0/ This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.
Porokeratosis (PK) is a chronic progressive disorder of keratinization characterized clinically by hyperkeratotic papules or plaques surrounded by a threadlike, elevated border that expands centrifugally. Pathogenesis involves heterozygous mutations in mevalonate kinase enzyme. The most common variants are disseminated superficial actinic porokeratosis (DSAP) and PK of Mibelli. All forms show a thin column of parakeratosis, the cornoid lamella, representing the active border. Dermoscopy reveals central brownish discoloration surrounded by a single hypopigmented band and a peripheral ‘white track’. Long-standing cases of PK may undergo malignant transformation. UV-protection and topical agents, such as 5-fluorouracil, imiquimod, calcipotriol, tretinoin and oral retinoids are helpful. To study the clinical and epidemiological pattern of PK and the clinico-dermoscopic and histopathological correlation of PK. A prospective cross-sectional study was conducted on the patients attending the dermatology outpatient department (OPD) over 9 months with suspected features of PK. These patients were evaluated clinically and subjected to dermoscopy and histopathology. Statistical Package for the Social Sciences (SPSS) Of 11 patients, there were four (36.36%) males and seven (63.66%) females. The youngest was 18-year-old boy, and the eldest was 63-year-old man. The clinically most common type was PK of Mibelli with five (45.45%) cases. The most common dermoscopic feature observed was double-marginated, white peripheral border. The most common histopathological feature noted was cornoid lamella. PK is a rare skin disorder with a wide spectrum of clinical variants. Dermoscopy and histopathology aid in diagnosis, whereas dermoscopy plays a pivotal role in early and non-invasive diagnosis. Regular follow-up is mandatory to watch for the development of malignancies in a few variants.

KEY WORDS:

Cornoid lamella
disseminated superficial actinic porokeratosis and porokeratosis of Mibelli
porokeratosis
==== Body
pmcIntroduction

Porokeratosis (PK) is a clonal expansion of keratinocytes which differentiate abnormally but are not truly neoplastic. It may present as single or multiple lesions and may be localized or disseminated. All forms show a thin column of parakeratosis, the cornoid lamella, representing the active border.[1] The most common variants of PK are disseminated superficial actinic porokeratosis (DSAP) and PK of Mibelli.[2]

Objectives – To study

1) Clinical and epidemiological pattern of PK.

2) Clinico-dermoscopic and histopathological correlation of PK.

Materials and Methods

A prospective cross-sectional study was conducted on the patients attending the dermatology outpatient department (OPD) over 9 months with suspected features of PK. They were evaluated clinically and subjected to dermoscopy and histopathology.

Results

Of 11 patients, there were four (36.36%) males and seven (63.66%) females [Table 1].

The youngest patient was 18-year-old boy, and the eldest was 63-year-old man.

The clinically most common type was PK of Mibelli with five (45.45%) cases, and other cases were four (36.36%) cases of DSAP, one (9.09%) case of PK palmaris et plantaris disseminata and one (9.09%) case of palmoplantar PK [Table 2].

The most common dermoscopic feature observed was double-marginated, white peripheral border.

The most common histopathological feature noted was cornoid lamella, thin column of tightly packed parakeratotic keratinocytes within a keratin-filled invagination of the epidermis through the stratum corneum.

The cornoid lamella on histology was corresponding to the double-marginated white peripheral border on dermoscopy in all cases.

Ultraviolet radiation exposure was the important risk factor for DSAP.

Table 1 Gender distribution among the study population

Gender	Frequency (%)	
FEMALE	7 (63.66)	
MALE	4 (36.36)	
TOTAL	11 (100)	

Table 2 Types of porokeratosis

Types of porokeratosis	Number (%)	
DSAP	4 (36.36)	
Porokeratosis of Mibelli	5 (45.45)	
Porokeratosis palmaris et plantaris disseminate	1 (9.09)	
Palmoplantar porokeratosis	1 (9.09)	

Case 1 – A 21-year-old woman presented with complaints of multiple, asymptomatic skin lesions over the face, neck and both upper limbs since 10 years.jpg significant family history was present. On examination, multiple, hyperkeratotic, annular papules surrounded by elevated border were present on the face, neck, bilateral arms and forearms [Figure 1a and b] On dermoscopy, double-marginated, white peripheral border with the central white area of scarring was seen [Figure 1c]. On histopathological examination, the epidermis shows keratinized stratified squamous epithelium with focal disruption of the granular layer, thin column of tightly packed parakeratotic keratinocytes within a keratin-filled invagination of the epidermis through the stratum corneum, cornoid lamella [Figure 1d]. The diagnosis of DSAP was made and was treated with oral isotretinoin 10 mg/day with topical tretinoin and sunscreens for 6 months. She was advised about strict sun protection and followed up regularly. There was a little bit of improvement in the appearance in the following visits.

Figure 1 (a-b) Multiple, hyperkeratotic, annular papules surrounded by elevated border on the face, neck, bilateral arms and forearms. (c) Dermoscopy 10X showing double-marginated, white peripheral border with the central white area of scarring. (d) H and E 40X showing keratinized stratified squamous epithelium with focal disruption of the granular layer, thin column of tightly packed parakeratotic keratinocytes within a keratin-filled invagination of the epidermis through the stratum corneum, cornoid lamella

Case 2 – A 30-year-old woman came with complaints of asymptomatic skin lesions over her nose since 4 years. Five hyperkeratotic, annular papules with elevated margins were noted over the left ala nasi and the left supralabial region. On dermoscopy, double-marginated white border was seen. She was diagnosed to have DSAP and treated with topical tretinoin cream and sunscreen.

Case 3 – A 36-year-old woman presented with skin lesions over the face since 1 year. Three hyperkeratotic, annular papules of size 0.5 cm in diameter, with raised margins, were present on the left ala nasi. On dermoscopy, double-marginated white border was seen. She was treated as DSAP with topical tretinoin cream and sunscreens.

Case 4 – A 32-year-old woman presented with skin lesions over her face since 5 years. One hyperkeratotic, annular plaque of size 3 cm × 3 cm present on the right ala nasi extending onto the right malar area with elevated borders was noted along with three hyperkeratotic, annular papules of size 0.5 cm in diameter, with raised margins on the left ala nasi and the left malar area. On dermoscopy, double-marginated white border was seen. She was treated as DSAP with topical tretinoin cream and sunscreens.

Case 5 – A 28-year-old woman came with complaint of asymptomatic skin lesion over her nose since 3 years. Solitary hyperkeratotic, annular papule of size 0.5 cm in diameter, with raised margins, was present on the left ala nasi. Dermoscopy demonstrated double-marginated white border. She was diagnosed to have PK of Mibelli and treated with sunscreens and topical tretinoin cream.

Case 6 – A 32-year-old woman presented with asymptomatic skin lesion on the face since 2 years. Solitary hyperkeratotic, annular papule of size 0.5 cm in diameter, with raised margins, was present on the right cheek. On dermoscopy, double-marginated white border was seen. The patient was treated as PK of Mibelli with topical 5-fluorouracil cream and sunscreens.

Case 7 – A 18-year-old male patient presented with the skin lesion on his chest since 5 years. Solitary hyperkeratotic, annular papule of size 0.5 cm in diameter, with raised margins, was present on the upper trunk. Dermoscopy of the lesion demonstrated double-marginated white border. He was diagnosed to have PK of Mibelli and treated with sunscreens and topical tretinoin cream.

Case 8 – A 62-year-old man presented with asymptomatic skin lesion on the left thigh since 12 years, started initially as a small papule and gradually progressed. Solitary, hyperkeratotic, annular plaque of size 4 cm*3 cm with raised margins was present on the left anterior thigh. On dermoscopy, double-marginated white border was seen. The diagnosis of PK of Mibelli was made and was treated with topical tretinoin cream. He was explained to do regular follow-ups. There was improvement in the appearance after a few months.

Case 9 – A 58-year-old man presented with asymptomatic skin lesion over the left knee since 15 years, started initially as a small papule and gradually progressed. Solitary, hyperkeratotic, annular plaque of size 4 cm*3 cm with raised margins was present on the left knee [Figure 2a]. On dermoscopy, double-marginated white border was seen [Figure 2b]. The diagnosis of PK of Mibelli was made and treated with topical tretinoin cream. He was kept under regular follow-ups. There was a little bit of improvement in the appearance in the following visits.

Figure 2 (a) Solitary, hyperkeratotic, annular plaque of size 4 cm *3 cm with raised margins was present on the left knee on the anterior aspect. (b) Dermoscopy 10X showing double-marginated, white peripheral border with the central white area of scarring

Case 10 – A 29-year-old man came with complaints of multiple asymptomatic skin lesions all over the body since childhood. History of similar complaints in brother and father was present. Numerous, hyperkeratotic, annular papules of size 0.5 cm in diameter with elevated margins were present on the face, chest, abdomen, back, bilateral palms and soles [Figure 3]. On dermoscopy, double-marginated white border was seen [Figure 3e]. Histopathological features were consistent with PK. The diagnosis of PK palmaris et plantaris disseminate was made. The patient was treated with oral isotretinoin 20 mg on alternative days along with sunscreens for 6 months. There was a little bit of improvement in the appearance in the following visits.

Figure 3 (a-d) Numerous, hyperkeratotic, annular papules of size 0.5 cm in diameter with elevated margins were present on the face, chest, abdomen, back, bilateral palms and soles. (e) Dermoscopy 10X showing double-marginated, white peripheral border with the central white area of scarring

Case 11 – A 68-year-old woman presented with multiple asymptomatic skin lesions on both palms and soles. Multiple, hyperkeratotic, annular papules surrounded by elevated border were present on bilateral palms and soles [Figure 4]. On dermoscopy, double-marginated white border was seen [Figure 4e]. Histopathological features were consistent with PK. The patient was diagnosed to have palmoplantar PK. She was treated with oral isotretinoin 10 mg/day for 3 months. There was a little bit of improvement in the appearance in the following visits [Table 3].

Figure 4 (a-d) Multiple, hyperkeratotic, annular papules surrounded by elevated border were present on bilateral palms and soles. (e) Dermoscopy 10X showing double-marginated, white peripheral border with the central white area of scarring

Table 3 Description of cases

Case no.	Age (in years)/sex	Number of lesions	Site	Morphological types	
1	21/F	Multiple	Face, neck and both upper limbs	DSAP	
2	30/F	5	Left ala nasi and the left supralabial region	DSAP	
3	36/F	3	Left alae nasi	DSAP	
4	32/F	4	Right ala nasi extending onto the right malar area, the left ala nasi and the left malar area	DSAP	
5	28/F	1	Left alae nasi	Porokeratosis of Mibelli	
6	32/F	1	Right cheek	Porokeratosis of Mibelli	
7	18/M	1	Chest	Porokeratosis of Mibelli	
8	62/M	1	Left thigh	Porokeratosis of Mibelli	
9	58/M	1	Left knee	Porokeratosis of Mibelli	
10	29/M	Numerous	Face, chest, abdomen, back, bilateral palms and soles	Porokeratosis palmaris et plantaris disseminata	
11	68/F	Multiple	Bilateral palms and soles	Palmoplantar porokeratosis	

Discussion

PK is a chronic progressive disorder of keratinization characterized by hyperkeratotic papules or plaques surrounded by threadlike, elevated border that expands centrifugally.[2] PK was first described by Neumann in 1875.[3] However, Mibelli described the classical form in 1893 and coined the term ‘PK’.[4] It is a clonal keratinizing disorder of uncertain aetiology.[5] Pathogenesis involves heterozygous mutations in mevalonate kinase gene, located on chromosome-12q24, inherited as autosomal dominant traits.[6] Ultraviolet light exposure, extensive radiation therapy, immunosuppression, transplant procedures, immunodeficiency syndromes, chronic renal failure, chronic liver disease, haematological malignancies, human immunodeficiency virus (HIV) and hepatitis C virus infection have been implicated in the pathogenesis.[7] PK is slightly commoner in males.[8] The lesions may be found anywhere on the body, most commonly extremities, rarely involving genitalia and groin even in disseminated form.[9] PK is mainly classified into localized and generalized forms. The common localized variants are classical PK of Mibelli, linear PK and punctate PK. Generalized variants are disseminated superficial porokeratosis (DSP), DSAP, DSP of immunosuppression, PK palmaris et plantaris disseminate and disseminated palmoplantar PK [Table 4].[2] Dermoscopy of porokeratotic lesions reveals central brownish discoloration with blue-grey dots, surrounded by a single hypopigmented band and a peripheral ‘white track’. Central scarring and enlarged capillaries are seen.[10] Histologically, PK is characterized by vertical column of tightly packed parakeratotic keratinocytes within an epidermal invagination called cornoid lamella, which results from either faulty maturation or acceleration of epidermopoiesis.[11] The granular layer is absent beneath the parakeratotic column. The involvement of the sweat pores explains the term ‘poro’ keratosis.[1] Differential diagnosis includes granuloma annulare, tinea corporis, actinic keratoses, elastosis perforans, lichen planus and Goltz syndrome. For linear lesions, differential diagnoses are linear inflammatory verrucous epidermal nevus, linear lichen planus, incontinentia pigmenti and ichthyosis linearis circumflexa.[2] Long-standing cases of PK may undergo malignant transformation (Bowen’s disease, squamous cell carcinoma, basal cell carcinoma and melanoma). Malignant transformation has been reported in 6.9% to 11.6% of cases.[12] Long-standing lesions, larger lesions and linear type are at high risk of developing malignancy. Hence, these patients should be monitored regularly for the risk of malignant transformations.[13] Other complications include ulceration, soft-tissue destruction, disfigurement, pseudo ainhum with amputation[7] and development of cutaneous horn.[14] Treatment includes sun protection and topical agents, such as imiquimod, calcipotriol, steroids and 5-fluorouracil. Other options are cryotherapy, photodynamic therapy, carbon dioxide laser and systemic retinoids.[15]

Table 4 Summary of porokeratosis subtypes[2]

	Inheritance and risk factors	Epidemiology	Clinical findings	Special concerns	
Porokeratosis of Mibelli	Autosomal dominant	Onset in infancy or childhood; male predominance	Asymptomatic, small brown to skin-coloured annular papules with an annular border	Large lesions have malignant potential	
Disseminated superficial actinic porokeratosis (DSAP)	Autosomal dominant	Most common porokeratosis; as early as childhood; female predominance	Uniform, small, annular, papules from 2–5mm, with symmetrical distribution on photoexposed extremities; asymptomatic or slightly pruritic	-	
Disseminated superficial porokeratosis	Autosomal dominant	Onset by third to fourth decade of life; female predominance	Uniform, small, annular, papules from 2–5mm, with symmetrical distribution on photoprotected sites; asymptomatic or slightly pruritic	-	
Disseminated superficial porokeratosis of immunosuppression	Immunosuppression after organ transplantation, drugs or infections	Dependent on exposure	Uniform, small, annular, papules from 2–5mm, with symmetrical distribution on photoexposed extremities; asymptomatic or slightly pruritic	-	
Linear porokeratosis	Mosaic manifestation of other porokeratosis variants	Uncommon; presents in early childhood	Primary manifestation dependent on particular variant, follows lines of Blaschko	Highest potential for malignant degeneration	
Porokeratosis palmaris et plantaris disseminata	Autosomal dominant	Adolescence or early adulthood; male predominance	Small, uniform lesions appearing on palms and soles with involvement to other sites; bilateral, symmetric involvement	-	
Punctate porokeratosis	Concomitant occurrence with other forms of porokeratosis	Adolescence or adulthood	Multiple discrete punctate hyperkeratotic lesions; may aggregate to form plaques	-	

Conclusion

PK is a rare skin disorder with a wide spectrum of clinical variants. Dermoscopy and histopathology aid in diagnosis, whereas dermoscopy plays a pivotal role in early and non-invasive diagnosis. PK is usually a benign dermatosis, except for some variants (linear and giant) where aggressive treatment is required to prevent the development of malignancies. Such patients should be explained about strict sun protection, use of sunscreens and chances of developing cutaneous malignancies. Regular follow-up is mandatory in such cases to watch for the development of malignancies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.
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