Chronic prurigo: A retrospective study of 168 cases

Chronic prurigo is classified into two clinical subtypes: prurigo nodularis (PN) and prurigo chronica multiformis (PCM) in Japan. In this study, we retrospectively investigated the clinical features of 168 patients with chronic prurigo (103 with PN and 65 with PCM) diagnosed at the Tokyo Medical and Dental University, and compared age, sex, prevalence of comorbidities, blood test results, histology and treatment efficacy in both groups. We found that patients with PCM were significantly older than those with PN. Males were more frequently diagnosed with PCM than females; however, both sexes were similarly affected by PN. Chronic infection was more prevalent in PN, whereas diabetes was more common in PCM. For both subtypes, serum immunoglobulin E levels were elevated above the normal range. However, serum thymus and activation-regulated chemokine/CCL17 levels and the number of blood eosinophils were significantly higher in patients with PCM than in those with PN. Histologically, much higher numbers of CD4⁺ cells than CD8⁺ cells were distributed in the lesions of both subtypes. Eosinophils were distributed predominantly in intracollagenous lesions in PCM but were observed mainly in perivascular lesions in PN. There were no differences in basophil and mast cell distributions in the lesions of the two groups. Treatment efficacy was also similar in both subtypes. Together, both subtypes exhibit inflammation patterns predominantly driven by T-helper 2 cells. With respect to PCM, elevated numbers of blood eosinophils and the recruitment of these cells into intracollagenous areas may be important for pathogenesis.