Psoriasis neurodermiformis, verrucous psoriasis, and psoriasiform keratosis: A clinicopathological evaluation

Abstract

Background: Psoriasis neurodermiformis (PN) and verrucous psoriasis (VP) are two distinct forms of psoriasis characterized by thickened plaques, whose proper description in most dermatologic texts is still lacking. Psoriasiform keratosis (PK) is a recently described clinical entity characterized by a solitary keratotic plaque whose microscopic findings simulate psoriasis. Aim: To compare and evaluate the clinical and histological profile of PN, VP and PK, and systematically characterize each of them. Settings and Design: This was a prospective, descriptive study done on a total of 51 patients, who were diagnosed with PN, VP and PK based on certain clinical criteria. The study was done at a teaching hospital in eastern India. Methods and Materials: The study was carried out on a total of 51 patients presenting with thickened psoriasiform plaques, who visited our outpatient department, over a period of 9 months. They were then carefully evaluated clinically (along with their demographic profile), followed by meticulous microscopic assessment. Each biopsy specimen was then categorically evaluated to enable a precise diagnostic conclusion. Statistical Analysis: As all values in our study were qualitative, they were expressed as numeric values and percentages. Results: Out of 51 patients, 18 were diagnosed as PN, 19 with VP and 14 with PK. PN demonstrated an equal gender distribution, whereas in VP and PK a male preponderance was apparent. History of past/present psoriasis was positive in only one patient diagnosed with VP. Intensity of pruritus was marked in 88.88%, 21.05% and 14.28% of patients with PN, VP and PK respectively. Dorsa of feet was the commonest site of involvement in PN and VP. In PK, the shin was the predominating site. VP presented clinically as mammillated, verrucous and crateriform phenotypes. PN and PK however, demonstrated single clinical patterns. Microscopically, none of the specimens satisfied all the 7 epidermal criteria set forth by Ackerman. In each slide Trozak’s histologic psoriasiform numeric score was >10. Conclusion: PN, VP and PK are certainly not as rare as previously considered. Mammillated VP closely mimics PN clinically. Crateriform VP is an extremely rare phenotypic expression encountered. Histological findings of papillomatosis, buttressing and anastomosing rete ridges and a dense dermal lymphocytic infiltrate point more in favor toward VP. Detecting solitary keratotic plaques with a psoriasiform histology should allow clinicians to consider the possibility of PK.