Lupus nephritis presenting with positive PR3-ANCA and decreased ADAMTS13

ABSTRACT

Introduction: Lupus nephritis is a well-described entity. The simultaneous presence of ANCA abs is rare and is related to poor prognosis. Positive patients usually have MPOANCA. We present a case of biopsy-proven Class IV/V Lupus nephritis with PR3-ANCA and decreased ADAMTS 13 activity in an AA man. Case Description This 46-year-old AA man with no known past medical history presented to the ED for two weeks of SOB, leg, and scrotal swelling. He denies any associated symptoms. He denies using any other OTC medications and illegal drugs. On exam, vital signs were stable. He had 2+ pitting edema in LE bilaterally, scrotal and penile edema. Other systems were unremarkable. Labs were significant for Hg 5.1, Platelets 106, K 6.9, CO2 9, BUN 78, Cr 10.2, and Albumin 2.4. UA showed dysmorphic RBCs and proteinuria, and Urine protein/creatinine of 9. COVID-19 testing was negative. HIV1&2, RPR titer, hepatitis panel, rheumatoid factor, ASO screen were all negative. Renal U/S showed normal-sized kidneys and no hydronephrosis. ANA, ANA titer, and anti-dsDNA returned elevated at >10,1640 and 9.9IU, respectively. PR3-ANCA was also positive, but MPO-ANCA negative. C3 and C4 at 0.4g/L and 0.14g/L, respectively. ADAMTS-13 activity decreased to 40%. The rest of the work-up was negative. Kidney biopsy confirmed lupus nephritis, Class IV, and V, with ∼50% cellular crescents. Moderate to advanced interstitial fibrosis and tubular atrophy ∼50%. EM showed two globally sclerotic glomeruli. IF showed a full-house with IgG, IgA, C3, C1q, kappa, and lambda. Unfortunately, kidney function did not recover, and hemodialysis was started, and he was treated with MMF, Methylprednisolone, and with plasma exchange. Discussion: ANCA positivity, although not common, is a well-described entity but not understood in lupus nephritis patients. Most of these patients present with MPO-ANCA rather than PR3-ANCA. This subset of patients usually presents clinically differently with distinct histopathological features. Long-term follow-up in these patients is also needed to better understand this disease process in lupus nephritis patients.