A study of clinicohistopathological correlation in patients of psoriasis and psoriasiform dermatitis.

BACKGROUND Psoriasis has different clinical variants, which mimic diverse dermatological conditions and may require a histopathological confirmation of the diagnosis. Studies to establish a clinicohistopathological concordance (and its determinants), in psoriasis and psoriasiform dermatitis are lacking. AIMS The present study was designed (a) to correlate the clinicohistopathological features of psoriasis and psoriasiform dermatitis, and (b) to identify determinant(s) that may contribute to the diagnosis of psoriasis and psoriasiform dermatitis. METHODS This was a prospective study involving 100 patients, with a single clinical diagnosis of psoriasis or with psoriasis as one of the differential diagnoses, and its correlation with histopathological features. RESULTS The clinical features of typical scale (P = 0.0001) and Auspitz's sign (P = 0.0001), and histological evidence of suprapapillary thinning (P = 0.0001) and absent granular cell layer (P = 0.0001) were found to be statistically significant contributors to the clinicohistological concordance in cases of psoriasis. Vertical orientation of collagen bundles (P = 0.0001) and lymphocytic exocytosis (P = 0.003) were found to be significantly associated with diagnosis of psoriasiform dermatitis. CONCLUSION The present study reconfirms the diagnostic accuracy of silvery white scale, Auspitz's sign, and Koebner's phenomenon in a clinical setting suggestive of psoriasis. However, in their absence, histological evidence of suprapapillary thinning and absent granular layer, in addition to the Munro microabscess and Kogoj's abscess, may contribute to the diagnosis of psoriasis. Similarly, vertical orientation of collagen bundles and lymphocytic exocytosis may point toward a diagnosis of psoriasiform dermatitis.