Eosinophilic granulomatosis with polyangiitis complicated with bullous pemphigoid.

Eosinophilic granulomatosis with polyangiitis (EGPA) and bullous pemphigoid (BP) are both autoimmune diseases characterised by eosinophilic involvement. Coexistence of the two diseases is rare, and confirmatory immunological analyses for BP are lacking in such cases. Here, we report a male in his 80s diagnosed with EGPA 5 years previously who developed numbness and tense blisters but showed no peripheral eosinophilia. The presence of anti-BP180 antibodies, subepidermal blistering with marked eosinophilic infiltration and immunohistochemical analysis of the blistering lesion confirmed a diagnosis of BP. High-dose prednisolone improved both blistering and neuropathic symptoms. This case underscores the rare overlap between EGPA and BP. Notably, the absence of peripheral eosinophilia despite marked tissue eosinophilic infiltration raises critical concerns regarding local eosinophil activation and the necessity for direct tissue analysis in such complex cases. Thus, both histopathological and immunological assessments are necessary to confirm such cases.