Immunoglobulin G4-Related Disease Presenting With Peripheral Neuropathy, Membranous Nephropathy and Interstitial Lung Disease: A Case Report.

Immunoglobulin G4-related disease (IgG4-RD) is a chronic, progressive inflammatory disease with fibrosis that affects multiple organs, while symptomatic peripheral nerve invasion is very rare. Here we present a Chinese male aged 77 years with peripheral neuropathy, membranous nephropathy, and interstitial lung disease diagnosed with IgG4-RD. The patient exhibited elevated levels of IgG4 and IgG4/IgG ratios in the blood. A chest computed tomography (CT) showed interstitial pneumonia in both lungs and multiple mediastinal lymphadenopathy. Additionally, electromyography shows neurogenic lesions in both lower extremities and axonal lesions involving motor nerves. Biopsies of the kidney showed membranous nephropathy with numerous IgG4-positive plasma cells. Patients treated with cyclophosphamide and high-dose methylprednisolone showed improvement in neuropathy, proteinuria, and interpulmonary severity. This case demonstrates the unusual presentation of IgG4-RD where peripheral neuropathy is the main feature with multisystem involvement but without mass lesions. It underscores the varied clinical manifestations of this disease.