Histopathologic diagnostic parameters of psoriasis; a clinicopathological study

Background: Psoriasis is a common inflammatory skin disorder comprised of varied histo-morphological features involving both epidermis and dermis. Further, there are psoriasiform lesions which simulate psoriasis. Hence it is mandatory to recognise psoriasis based on histopathological parameters to aid the treatment protocol.Methods: Sixty cases of histopathologically confirmed psoriasis vulgaris and pustular psoriasis excluding psoriasiform dermatitis, reported in the Department of Pathology, over a period of 6 years were analysed. The sections were stained with hematoxylin and eosin stains and analyzed for various morphological parameters. Results: Out of 60 cases 88.33% were psoriasis vulgaris and 11.67% were pustular psoriasis. Age incidence was high in second and fourth decades with male predominance. The commonly involved sites were upper and lower extremities. Significant histopathological parameters were parakeratosis (100%), hyperkeratosis (100%), spongiosis (91.67%), and papillomatosis (73.33%), either hypogranulosis (55%) or agranulosis (45%), and dilated and tortuous capillaries (88.33%, 43.33% respectively) in the dermis. Conclusions: Histopathological correlation is still the gold standard tool for the diagnosis of psoriasis. In the absence of well-formed Munro microabscess and pustules of Kogoj, other epidermal features like parakeratosis, hyperkeratosis, spongiosis, papillomatosis and absent or thinned out granular layer as well as dilated and tortuous capillaries in the dermis can be considered as confirmatory evidence of psoriasis. The reduction or complete absence of granular layer was characteristic of psoriasis and reflected the pathogenesis of defective keratinocyte proliferation.