Coexistence of porokeratosis ptychotropica with porokeratosis of Mibelli in a Chinese man

Porokeratosis represents a spectrum of clinical diseases. Multiple variants have been described including porokeratosis ptychotropica, a rare subtype. The coexistence of two or more variants of porokeratosis in a single patient is regarded as a rare occurrence. Here we report a patient with porokeratosis ptychotropica with coexistent porokeratosis of Mibelli. The patient was a 47-year-old man who presented with a month’s history of pruritic rash on the buttocks. The patient also had an asymptomatic cutaneous eruption involving his right lower part of the buttocks of 20 years’ duration. There was no family history of a similar eruption. On physical examination, the patient had perianal erythematous papules and plaques with scale which were coalescent in several locations and extended bilaterally onto the buttocks. The examination also demonstrated satellite papules. His right lower part of the buttocks demonstrated annular patches with a peripheral keratotic ridge. The areas had a diameter of 6 cm in size (Figure 1). A skin biopsy of these two different lesions was performed. Histopathological examination of perianal erythematous papules showed characteristic multiple cornoid lamellae (Figure 2). Dyskeratotic cells and focal hypogranulosis were present in the epidermis underlying the column of parakeratosis. The upper dermis contained a mild perivascular lymphocytic infiltrate. No amyloid deposition was seen (Figure 3). The clinical and pathologic findings were compatible with a diagnosis of porokeratosis ptychotropica. The annular patches of his right lower part of the buttocks showed cornoid lamellae at the periphery (Figure 4). Dyskeratotic cells and focal hypogranulosis were present in the epidermis underlying the column of parakeratosis. The annular patches were consistent with a diagnosis of porokeratosis of Mibelli. Porokeratosis represents a disorder of epidermal keratinization. Its exact aetiology has not been well established but there is increasing evidence that implicates aberrant terminal differentiation of keratinocytes [1]. Porokeratosis is characterized by the cornoid lamella, a column of tightly packed parakeratotic cells that reside within a depression of the epidermis. The cornoid lamella is seen in all variants of porokeratosis, but it is not pathognomonic for the disorder [2].