Nonlupus Full-House Nephropathy Presenting with Rapidly Progressive Glomerulonephritis, Hypertensive Emergency, and Heart Failure

Introduction: Nonlupus full house nephropathy (NLFHN) is a rare and heterogenous clinical entity that is distinct from lupus nephritis. Here, we describe a case of NLFHN presenting with rapidly progressive glomerulonephritis and hypertensive emergency with new onset systolic heart failure. Case Description: A 43-year-old male with a past medical history only of COVID-19 infection presented with several weeks of headaches, blurry vision, and leg swelling. He was found to have severely elevated blood pressure (224/138 mmHg), severe hypertensive retinopathy, and 3+ pitting lower extremity edema. Laboratories revealed serum creatinine 3.8 mg/dL, serum albumin 2.8 g/dL, hematuria (682 RBC/hpf), and proteinuria (UACR 7723 mg/g). Echocardiogram revealed moderately reduced left ventricular systolic function with ejection fraction 35-40%. Serologies were notable for low total complement and low-normal C3 complement levels, elevated rheumatoid factor, and negative ANA and dsDNA antibodies. Kidney biopsy revealed a light microscopy pattern of membranoproliferative glomerulonephritis with cellular crescents and a full house pattern on direct immunofluorescence with 3+ staining for IgG, 3+ IgM, 2+ IgA, 3+ C3, and 1+ C1q. Workup for secondary causes was negative including testing for HIV, syphilis, hepatitis B/C, anti-neutrophil cytoplasmic antibody, and cryoglobulin. Discussion: NLFHN is an immune complex glomerulonephritis that can present with different light microscopy patterns accompanied by a typical full-house immunofluorescence pattern, without clinical or laboratory features of lupus. It can be categorized as secondary or idiopathic. Secondary causes include infections, autoimmune diseases, lymphoid neoplasms, or drugs. NLFHN typically has male predominance, higher proteinuria, and less complement consumption than lupus nephritis. Our case highlights that NLFHN can present with clinically challenging conditions including rapidly progressive glomerulonephritis, hypertensive emergency, and heart failure. While a preceding viral illness may have been causative, the patient is being followed for the potential development of an overt autoimmune condition with ANA and dsDNA every 6 months. He is doing well with a partial renal response and recovered left ventricular systolic dysfunction on mycophenolate and tapered prednisone.