Membranoproliferative Glomerulonephritis (MPGN) in the Setting of Unicentric Castleman Disease

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Introduction: Castleman’s disease (CD) is a rare lymphoproliferative disorder with histopathological abnormalities - divided primarily into unicentric and multicentric disease. Thought to be an inflammatory process, renal involvement has been described extensively in the setting of multicentric disease, especially associated with HHV-8. However, similar reports in unicentric disease are rather limited. Case Description: A 33 year old female with asthma developed hematuria and proteinuria in the setting of chronic right flank pain and intermittent night sweats for about 2 years. With a stable creatinine (Cr) level of 0.7 mg/dL, blood work was negative for C3, C4, cryoglobulins, and hepatitis panels. UA showed no hematuria, but did reveal 0.6 - 1.0 g of proteinuria. Imaging revealed 2 mesenteric soft tissue nodules, largest measuring 2.4 cm. A renal biopsy was significant for immune complex MPGN with kappa and c3. PET-CT at 1 year revealed hypermetabolic mesenteric nodules suspicious for malignancy. Nodular biopsy showed atypical B-lymphoid infiltrate initially concerning for marginal cell lymphoma. Referral to Mayo Clinic was confirmatory for hyaline vascular unicentric Castleman’s disease. HHV8, PCR for B-cell receptor gene rearrangement and FISH for t(11;18) were negative. Referral made to Rheumatology for MPGN and moderate concern for systemic lupus erythematosus (SLE) with ANA 1:160 and BC4d, however no systemic symptoms of SLE. Follow-up imaging showed a decrease in lymphadenopathy from 2.3 to 1.6 cm, with plan for conservative management. Patient’s proteinuria persisted at 821.5 mg with plan for ACE inhibitor but avoided in the setting of the patient’s third pregnancy. Discussion: Renal involvement is typical in multicentric CD so, we present a unique case of unicentric CD associated with MPGN. Persistent proteinuria and MPGN with ANA 1:160 and BC4d placed lupus nephritis versus Castleman’s induced nephropathy on the differential. However, lack of SLE symptoms, normal complement and double stranded DNA indicated a unique disease presentation of Castleman’s with proteinuria.

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