Resistant palmoplantar lesions in patients of psoriasis: evaluation of the causes and comparison of the frequency of delayed-type hypersensitivity in patients without palm and sole lesions.

Objective: To examine the reasons for resistance to treatment in cases of palmoplantar psoriasis, and also to compare the frequency of delayed-type hypersensitivity to common sensitizers with those cases of psoriasis without palmoplantar involvement.

Subjects And Methods: One hundred and three patients with resistant palmoplantar psoriasis were examined for a possible drug reaction, fungal infection or contact allergy. Patch testing was done for another 100 patients with psoriasis vulgaris without palm and sole involvement. χ(2), Fischer's exact test, Mann-Whitney U test and logistical regression analysis were done using SPSS 15.0.

Results: Of the 103 patients with resistant palmoplantar lesions, 26 (25.24%) had a positive patch test to at least one of the tested allergens, 6 (5.8%) had psoriasiform spongiotic dermatitis on biopsy, 5 (4.8%) reported exacerbation after starting biologic therapy and 3 (2.9%) were potassium hydroxide positive in the sole lesions. In comparison, of the 100 patients with no palm or sole lesions, 11 (11%) had a positive patch test to at least one of the allergens. There was a direct relationship between the increase in the prevalence of dermatitis and the duration of psoriasis. There was no correlation between the clinical type of psoriasis and patch-test positivity.

Conclusion: Secondary fungal infection, allergic contact dermatitis to topical agents or common allergens, or at times an unusual reaction to the antipsoriatic therapeutic agents sometimes led to treatment failure in patients with psoriasis vulgaris with palmoplantar lesions. Also, psoriasis patients with palm and sole lesions tended to have higher rates of contact hypersensitivity than patients without lesions on their palms and soles.