Segmental Porokeratosis Pigmentosa - An Unusual Presentation of Porokeratosis or a New Entity?

A 3 year old boy presented with complaints of darkening of skin along the right side of body for the past 2 years, progressively increasing in size and pigmentation. Cutanoues examination revealed multiple hyperpigmented linearly arranged macules and annular plaques following the lines of Blaschko anteriorly running along the right side of the body extending from the axilae to the inguinal and face. The macules and plaques on the body and extremities were hyperpigmented with atrophy in the centre with raised hyperkeratotic borders. We made a clinical diagnose of LinearPorokeratosis and a skin biopsy confirmed the diagnosis, which showed hyperkeratosis and typical coronoid lamella tightly stacked with parakeratotic cells along with increased amount of melanin in the basal layer and mild lymphocytic infiltration into the dermis. The diagnosis of Porokeratosis was confirmed and the boy has been under our treatment ever since for the past 1 year. We report this case for its rarity and even though this case if classified in the existing classification fits more into the Linear variant of porokeratosis, hyperpigmentation in porokeratosis has not been reported before. With the histological findings showing increased amount of melanin in the basal layer along with other findings of porokeratosis we could also consider this case as a new clinical variant which we have named as segmental porokeratosis pigmentosa.