Malignant Transformation in Porokeratosis Ptychotropica: A Systematic Review

Abstract

Porokeratosis ptychotropica (PP) is a rare and unusual variant of porokeratosis. There is a dearth of information on the natural history, epidemiology, and optimal treatment options. This study aimed to characterize the worldwide distribution, epidemiology, clinical features, and treatments attempted for all reported cases of porokeratosis ptychotropica. A total of 59 cases of porokeratosis ptychotropica have been reported, with most cases originating from the United States. The median age of patients affected with porokeratosis ptychotropica was 49 years. The most involved body locations are the buttocks and gluteal cleft. The risk of malignant transformation in porokeratosis ptychotropica is approximately 1.7% but there is significant bias in estimating rare occurrences in rare diseases. In conclusion, PP is an important but under-recognized variant of porokeratosis, with a likely low risk of malignant transformation. The best available treatment modality remains uncertain; however, the use of topical lovastatin/cholesterol cream appears promising. Long-term surveillance appears prudent for porokeratosis ptychotropica due to a risk of cancerization.

Fig. 1

Verrucous pink plaques over the gluteal folds, surrounded by satellite red-brown papules with a peripheral hyperkeratotic rim.

Fig. 2

(A) Low-power view showing epidermal hyperplasia with columns of parakeratosis (arrows) and mild dermal superficial perivascular infiltrate of lymphocytes (haematoxylin & eosin 40x magnification). (B) High-power view showing column of parakeratosis (cornoid lamella) with loss of granular layer and underlying dyskeratotic keratinocytes (haematoxylin & eosin 200x magnification).

Fig. 3

Frequency heat map of reported cases of porokeratosis ptychotropica.