Cryoglobulinemic Glomerulonephritis as a Presentation of Atypical Post-Infectious Glomerulonephritis

Post-infectious glomerulonephritis (PIGN) usually occurs within few days to weeks following an infection. Clinical presentation is variable, but in general, it is considered a benign entity with good prognosis. It rarely requires kidney biopsy to confirm the diagnosis. We present a case of a 55-year-old, previously healthy, male who presented for worsening shortness of breath, persistent cough, and right-sided pleuritic chest pain. Initial workup revealed a right exudative effusion with empyema. Hospital course was complicated by acute kidney injury requiring renal replacement therapy with a peak creatinine of 10.2 mg/dL from a baseline of 1.18 mg/dL. On kidney biopsy, findings were compatible with a diagnosis of cryoglobulinemic glomerulonephritis or an atypical form of PIGN. While a wide variety of histopathological findings on renal biopsies have been described to complement the usual diffuse proliferative glomerulonephritis pattern, cryoglobulinemic features with negative cryoglobulin have never been reported. Our case is unique not only by having an atypical histological presentation but also by meeting the criteria of atypical PIGN with persistent hypertension and microscopic hematuria.