Cryoglobulinemic Glomerulonephritis Masquerading as IgA Nephropathy in a Patient with Crohn Disease

Introduction: We report a case of a patient with long standing history of Crohn’s presenting with anemia, acute renal failure requiring initiation of dialysis and lower extremity painful rash. Renal biopsy initially suggested IgA nephropathy given history of Crohn’s and codominant IgA and IgM, but EM features and serological markers made cryoglobulinemic GN a favorable diagnosis. In this case, we address the diagnostic complexity we came across. Case Description: This is a 48-year-old Caucasian female who was admitted with anemia, acute kidney injury, and purpuric rash of the lower extremities. Urinalysis revealed red blood cells and nephrotic range proteinuria. Urine sediment showed RBC casts. Renal function rapidly deteriorated requiring initiation of dialysis. Physical exam revealed painful LE purpuric rash, levido reticularis and dorsal foot ulcers. Imaging showed ground glass opacities. Given the rapid decline in renal function and findings suggestive of systemic vasculitis, a renal biopsy was expedited. Biopsy showed focal necrotizing and crescentic glomerulonephritis on LM, IF staining with +1 IgA ,IgM and +2 C3 staining. However, there were rare subendothelial and mesangial electron dense deposits with curvilinear substructure on EM suggesting cryoglobulinemic GN. Serological markers came back positive for rheumatoid, borderline low C3 with normal C4 and serum cryoglobulin was positive, with immunofixation showing type 2 mixed cryoglobulins. Broad work up was done to identify an infectious or lymphoproliferative etiology of cryogenesis revealing a positive respiratory culture growing Klebsiella pneumonia on BAL, and pleural nodule biopsy showed organizing pneumonia. The patient was promptly started on pulse steroids, IVIG and PLEX with improvement in skin rash. She continued to require dialysis on discharge, and Rituximab was deferred to the outpatient setting due to active infection. Discussion: Cryoglobulinemic glomerulonephritis (GN) is a disorder characterized by the deposition of cryoglobulins. Cryoglobulinemic and IgA vasculitis can have multiple similarities in clinical and pathological features. In this case we encountered multiple overlapping clinical and histological findings, but ultimate diagnosis was favorable for cryoglobulinemic vasculitis. The positive rheumatoid and EM findings helped in making the distinction.