Peripheral eosinophilia in bullous pemphigoid: prevalence and influence on the clinical manifestation

Background: Peripheral eosinophilia has been reported in 50–60% of patients with bullous pemphigoid (BP) and correlated positively with disease severity. Objectives: To establish an association of peripheral eosinophilia with the different morphological characteristics of BP. Methods: The study was designed as a case–control study. Diagnosis of BP was grounded on well-established immunopathological criteria. Five age-, sex- and ethnicity-matched controls were randomly selected for each patient with BP. Results: Overall, 225 patients with BP and 1125 control participants were enrolled. A total of 113 (50·2%) patients with BP and 49 (4·4%) controls had pathological peripheral eosinophilia (P < 0·001). An independent association between eosinophil count and the diagnosis of BP was observed [odds ratio 59·9 (per 1000 eosinophil μL⁻¹ increase); P < 0·001]. Patients with BP with eosinophilia were significantly older at presentation (P = 0·003) and had increased palmoplantar involvement (P = 0·005), whereas patients with normal eosinophil counts had greater involvement of mucosal surfaces (P = 0·002) and the head and neck (P = 0·047). Patients with BP with extensive disease had significantly higher eosinophil counts than patients with mild-to-moderate disease (996·5 ± 1052·5 vs. 696·1 ± 962·6 cells μL⁻¹; P < 0·001). Conclusions: Patients with BP with serum eosinophilia were significantly older and had higher palmoplantar involvement. Patients with BP with a normal eosinophil count were younger and presented more frequently with atypical clinical manifestations.