Porokeratosis in Singapore: an Asian perspective

Porokeratosis is a rare disorder of skin keratinisation characterised by a cornoid lamella. We reviewed its associations with immunosuppression and phototherapy, as well as the risks of malignant progression. This is a retrospective review on all cases of porokeratosis seen at the National Skin Centre, Singapore, between 2000 and 2010. A total of 94 patients were reviewed. Clinical and histological diagnoses were confirmed in 63% patients. Most patients were Chinese (89%) with a mean age of 51.6 years. The male to female ratio was 1.4:1. The four main clinical variants were classical porokeratosis of Mibelli (56%), disseminated superficial actinic porokeratosis (DSAP) (18%), disseminated superficial porokeratosis (DSP) (11%), and linear porokeratosis (13%). Phototherapy-induced porokeratosis, seen in three patients, is rare. Seven cases of porokeratosis occurred in patients who were immunosuppressed. Progression of porokeratosis to malignancy is uncommon and was observed in three patients. The most common treatments included cryotherapy (26.5%) as well as topical steroids or retinoids (38.1%). A good response, defined as clear or almost clear lesions, occurred in 16% patients. The most common presentation of porokeratosis in our review was a middle-aged male patient with an asymptomatic lesion of porokeratosis of Mibelli over the extremities. No particular immunosuppressive drug was implicated. Porokeratosis associated with ultraviolet phototherapy or malignancy is rare. Progression of porokeratosis to malignancy arose in the disseminated variants, with a possible correlation with age. This is the largest institutional retrospective review of porokeratosis to date and highlights the major epidemiological characteristics of this condition.