Porokeratoses (overview) Q82.8

The term "porokeratosis" is used to describe a group of diseases with great genetic heterogeneity and clinical diversity, which is characterized by a superordinate pathogenetic principle, the formation of a focal, vent-shaped parakeratosis (so-called cornoid lamella). The name "porokeratosis" is undoubtedly a misnomer, as the "skin pore" is not the place of origin of the parakeratotic horny cone. However, it has found its way into international literature.

Clinically, the individual clinical pictures are characterized by the formation of keratotic papules with centrifugal growth and central atrophic flattening, resulting in characteristic, reddened, ring-shaped, horny papules or plaques with accentuated edges. In porokeratosis mibelli, map-like formations may also develop. In disseminated superficial porokeratosis, itchy, flat, often also annular papules and plaques are found, usually caused by actinic factors.

Characteristic is the histological phenomenon of the so-called " cornoid lamella", which is detectable in the area of the ring-shaped marginal ridge.

The following clinical variants with differing clinical morphology, acuity and localization have been described:

• Porokeratosis Mibelli (Porokeratosis 1)
• Porokeratosis plantaris, palmaris et disseminata (PPPD, Porokeratosis 2)
• Porokeratosis superficialis actinica disseminata (DSAP; porokeratosis types 3-9: uniform phenotype with numerous different genotypes)
• Superficial disseminated porokeratosis (SDP)
• Eruptive disseminated porokeratosis (EDP)
• Porokeratosis linearis unilateralis (linear porokeratosis, epidermal hamartoma)
• Porokeratosis punctata (PP)
• Porokeratosis punctata palmaris et plantaris is classified under the palmoplantar keratoses: palmoplantar keratosis punctate, type 2)

as well as some variants that require further confirmation

Other very rare clinical variants are (Le C, Bedocs PM 2021):

• Porokeratosis plantaris discreta
• Porokeratosis perforans
• Eruptive pruritic papular porokeratosis
• Reticular porokeratosis
• Giant porokeratosis
• Porokeratoma (Walsh 2007)
• Follicular porokeratosis (occurrence of cornoid lamellae in follicles; variant of disseminated actinic porokeratosis)
• Porokeratosis ptychotropica (inverse form localized in large folds and on genitalia).

m>f

Porokeratoses are associated with mutations in different gene loci (see classification).

The characteristic feature of porokeratoses is the so-called cornoid lamella, a columnar parakeratosis within an epidermis that is keratinized orthokeratotically.

Disease patterns summarized under the term "porokeratosis" with important distinguishing criteria

1. Agarwal S et al (2002) Porokeratosis of Mibelli: successful treatment with 5% imiquimod cream. Br J Dermatol 146: 338-339
2. Apel HP et al (1986) Porokeratosis linearis unilateralis (Linear porokeratosis). Dermatologist 37: 284-286
3. Arranz-Salas I et al (2003) p53 alterations in porokeratosis. J Cutan Pathol 30: 455-458.
4. Gotz A et al (1999) Porokeratosis Mibelli gigantea: case report and literature review. Dermatologist 50: 435-438
5. Itin PH et al (1995) Porokeratosis plantaris, palmaris et disseminataa with multiple filiform hyperkeratoses and nail dystrophy. Dermatologist 46: 869-872
6. Karthikeyan K et al (2003) Porokeratosis of mibelli with nail dystrophy. J Dermatol 30: 420-422
7. Kaur S et al (2002) Co-existence of variants of porokeratosis: a case report and a review of the literature. J Dermatol 29: 305-309
8. Lacarrubba F et al (2021) Porokeratosis ptychotropica: dermoscopy, reflectance confocal microscopy, and histopathological correlation. Indian J Dermatol 66: 540-542.
9. Le C, Bedocs PM (2021) Disseminated superficial actinic porokeratosis. 2020 Aug 10. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing PMID: 29083728.
10. Leman J et al (2001) A rare case of congenital porokeratosis. Clin Exp Dermatol 26: 728-729.
11. Liu P et al (2008) Identification of a genetic locus for autosomal dominant disseminated superficial actinic porokeratosis on chromosome 1p31.3-p31.1. Hum Genet 123:507-513.
12. Navarro V et al (2000) Facial superficial porokeratosis. Dermatology 201: 361
13. Nayeemuddin FA et al (2002) Topical photodynamic therapy in disseminated superficial actinic porokeratosis. Clin Exp Dermatol 27: 703-706
14. Porter WM et al (2001) Porokeratosis of the penis. Br J Dermatol 144: 643-644.
15. Taylor AMR et al (1973) Chromosomal instability associated with susceptibility to malignant disease in patients with porokeratosis of Mibelli. J Nat Cancer Inst 51: 371-378.

16. Vargas-Mora P et al (2020) Porokeratosis: A Review of its Pathophysiology, Clinical Manifestations, Diagnosis, and Treatment. Actas Dermo-Sifiliográficas (English Edition) 111: 545-560.

17. Vergara G et al (2002) Porokeratosis of the lower lip. Eur J Dermatol 12: 500-502.
18. Walsh SN et al (2007) Porokeratoma. Am J Surg Pathol 31:1897-1901.
19. Xia K et al (2002) A novel locus (DSAP2) for disseminated superficial actinic porokeratosis maps to chromosome 15q25.1-26.1. Br J Dermatol 147:650-654.
20. Zhang Z et al (2015) Genomic variations of the mevalonate pathway in porokeratosis. eLife 4: e06322.