IGHG3 and systemic lupus erythematosus: The predominant IgG subclass in pMNs is IgG4, and positive staining for IgG1, IgG3, IgA, or IgM, or significant luminescence in the mesangium, suggests the presence of Systemic Lupus Erythematosus (SLE) or another cause of sMN [11].