An Unusual and Rare Case of a Seronegative Male Patient With Lupus Nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect nearly every organ system. The 2019 European League Against Rheumatism and American College of Rheumatology (EULAR/ACR) SLE have proposed an additive, weighted multicriteria system for classifying SLE while using antinuclear antibody (ANA) as an entry criteria. Most patients with SLE will test positive for ANA. We report a 28-year-old half Caucasian and half Asian male patient who initially presented with malar rash, severe bilateral lower extremity edema, and proteinuria. Typical serological tests associated with SLE were negative. The diagnosis of seronegative lupus nephritis was made with kidney biopsy that revealed class IV and V lupus nephritis. Creatinine improved from 2.06 to 0.87 mg/dL with oral mycophenolate mofetil (MMF) and a tapered dose of glucocorticoids. This case highlights the difficulty of diagnosis and treatment of seronegative lupus nephritis.