Glucocorticoids Combined with Methotrexate in the Treatment of Psoriasis Merged with Bullous Pemphigoid: A Case Report and Literature Review

This case report describes the diagnosis and treatment of a 64-year-old male patient with psoriasis complicated by Bullous Pemphigoid (BP). The patient developed new-onset tension blisters on chronic psoriatic plaques, with coexistence confirmed by histopathology and direct immunofluorescence. A combined regimen of methylprednisolone and methotrexate resulted in the complete extinction of skin lesions after three months. Literature integration revealed: 1) Th17/Th2 immune imbalance is a pivotal mechanism, where IL-17A may degrade BP180 antigen via MMP-9 upregulation; 2) Early corticosteroid-immunosuppressant therapy effectively controls disease activity, yet 30–40% of patients relapse during corticosteroid tapering; 3) Long-term management should integrate lesion assessment, laboratory monitoring, and psychological intervention. This case offers clinical insights into this rare comorbidity and highlights BP induction risks associated with immunomodulatory therapies.