Psoriasis‐like skin rash triggered by a local infection in a patient with eosinophilic granulomatosis with polyangiitis that was well controlled by mepolizumab treatment

KEY CLINICAL MESSAGE: A patient with eosinophilic granulomatosis with polyangiitis, who was well‐controlled by pharmacotherapy, developed a psoriasis‐like rash due to a local infection. It represents the consequence of an immunologic imbalance. ABSTRACT: A 48‐year‐old woman was diagnosed with eosinophilic granulomatosis with polyangiitis and treated with mepolizumab. While on treatment, she developed a psoriasis‐like rash on her lower legs following a local ear infection. The rash promptly disappeared after the ear infection cleared and did not recur. The psoriasis‐like rash that appeared was pathologically similar to psoriasis. Excessive production of inflammatory cytokines by the immune system is believed to be involved in the pathogenesis of psoriasis vulgaris. These cytokines are known to induce inflammatory responses and promote epidermal cell proliferation. It is possible that mepolizumab treatment suppressed Th2‐type cytokines, while the local ear infection temporarily induced a strong Th1‐type immunity. This immunologic imbalance may have led to the development of a psoriasis‐like rash.