Pemphigus-like hypereosinophilic syndrome with FIP1L1-PDGFRA fusion gene: A challenging and uncommon clinical presentation.

Hypereosinophilic syndrome (HES) is often associated with cutaneous manifestations, mostly pruritic lesions, urticaria and angioedema. Mucosal lesions are rarely seen in HES but, when present, are usually the first manifestation of the disease. The clinical presentation may be heterogeneous, including erosions, aphthae or ulcers, and can be easily confused with other mucocutaneous disorders. Here, we present the case of a 64-year-old man with severe chronic erosive oral mucositis simulating pemphigus in which the finding of persistent eosinophilia and elevation of B12 vitamin serum levels raised the suspicion of HES. The FIP1L1-PDGFRA fusion gene (4q12) was detected by fluorescence in situ hybridization and the patient was treated with imatinib mesylate with complete response of the disease.