Author: Dr Karen Koch, Consultant Dermatologist, Wits University Donald Gordon Medical Clinic, Johannesburg, South Africa. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell/Maria McGivern. September 2018.
Porokeratosis ptychotropica is a rare form of porokeratosis that was first described in 1995. It presents as scaly or warty patches on the buttocks .
Men are nine times more affected by porokeratosis ptychotropica than women, and the average age of onset is 46.7 years (the reported age range is 27–84 years) .
The exact cause of porokeratosis ptychotropica is not known . Other forms of porokeratosis have been associated with risk factors such as exposure to ultraviolet radiation, trauma, renal and liver failure, organ transplantation, and immune suppression .
With other variants of porokeratosis, a genetic predisposition has been described; however, no genetic predisposition is known for porokeratosis ptychotropica, possibly due to its rareness .
Porokeratosis ptychotropica presents as warty or scaly plaques on the buttocks.
Porokeratosis ptychotropica can be difficult to diagnose, leading to a delay in treatment .
The differential diagnosis of porokeratosis ptychotropica includes:
There is no known cure for porokeratosis ptychotropica, and the results of treatment are generally disappointing. The appearance may improve with the following measures:
Porokeratosis ptychotropica tends to persist. In other forms of porokeratosis, there is a small risk of transformation to skin cancer. Regular follow-up of such skin lesions is recommended .
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