While the majority of patients in these studies were diagnosed with B-cell non-Hodgkin lymphomas (NHLs), a subset presented with other conditions, including neurological disorders (aquaporin-4-positive neuromyelitis optica spectrum disorder), hematologic autoimmune disease (immune thrombocytopenic purpura), dermatologic disease (pemphigus vulgaris), renal involvement (fibrillary glomerulonephritis, lupus nephritis with thrombotic microangiopathy) and systemic autoimmune disorders (systemic sclerosis, ANCA-associated vasculitis, primary Sjögren’s syndrome). This evidence concerns the gene AQP4 and lupus nephritis.