Porokeratosis ptychotropica Q82.8

Lucker GP et al, 1995

Very rare, clinical (inverse) manifestation form of disseminated superficial porokeratosis (from ptych=fold) with involvement of the major body folds (see porokeratoses below).

m>w

Unknown. A genetic disposition has not yet been proven with certainty, although heterozygous pathogenic mutations in the mevalonate kinase gene (MVK) (NM_00043.4>G p.L265R) have been detected in individual cases. Other forms of porokeratosis have been associated with risk factors such as UV radiation, trauma, kidney and liver failure, organ transplantation and immunosuppression.

The mean age of onset is 46.7 years (the reported age range is 27-84 years) (Takiguchi RH et al. 2009).

The skin lesions often affect the gluteal folds and the perianal region, which are often arranged in a symmetrical "butterfly" pattern. Rarely, the lower extremity is also affected. The scrotum or penis are rarely affected (Akay BN et al. 2025).

In disseminated, but also extensive distribution (often in a symmetrical butterfly-shaped pattern), reddened or also non-inflammatory brown-yellowish, slightly scaly, flat raised, also psoriasiform or verrucous papules and plaques are found. Itching has been reported.

Bioptic confirmation of the diagnosis. Histologically groundbreaking is the detection of a cornoid lamella. This is a parakeratotic column overlying a small vertical zone of dyskeratotic and vacuolated cells within the epidermis.

Psoriasis inversa

Dyskeratosis follicularis

Tinea corporis

Intertrigo

There is no known cure for porokeratosis ptychotropica and the results of treatment are generally disappointing. The appearance may improve with the following measures:

• 5-Fluorouracil cream
• Imiquimod cream
• Calcipotriol cream
• Isotretinoin

Individual foci can also be treated by cryosurgery or dermabrasion. Ablative laser systems can also be used.

Clinical monitoring is recommended, as the risk of malignant transformation cannot be ruled out.

1. Akay BN et al. (2025) UV-induced fluorescence dermatoscopy in a case of porokeratosis ptychotropica. J Dtsch Dermatol Ges 23:520-522.

2. Feng Y et al.(2021) Porokeratosis ptychotropica on the buttocks. Indian J Dermatol Venereol Leprol 7:1.
3. Lacarrubba F et al. (2021) Porokeratosis Ptychotropica: Dermoscopy, Reflectance Confocal Microscopy, and Histopathological Correlation. Indian J Dermatol 66: 540-542.
4. 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.
5. Lucker GPet al. (1995) An unusual case of porokeratosis involving the natal cleft: porokeratosis ptychotropica? Br J Dermatol 132: 150-151.
6. McGuigan K et al (2009) Porokeratosis ptychotropica: a clinically distinct variant of porokeratosis. J Am Acad Dermatol 60: 501-503.
7. Takiguchi RH et al (2009) Verrucous porokeratosis of the gluteal cleft (porokeratosis ptychotropica): a rare disease easily misdiagnosed. J Cutan Pathol 37: 802-807.
8. Tebet AC et al (2016) Porokeratosis ptychotropica. An Bras Dermatol 91: 134-136.
9. 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.