An 86-year-old man with history of hypertension (HTN), chronic obstructive pulmonary disease (COPD), and allergic rhinitis presented with one-week history of nausea, vomiting, diarrhea, and abdominal pain. Home medications included albuterol inhaler, carvedilol, hydralazine, and losartan. In the emergency department, he was found to be hypertensive with a blood pressure (BP) of 194/70 mm Hg and was mildly respiratory hypoxic with pulse oximetry reading of 89% on room air. Physical exam was significant for crackles at lung bases and 1+ bilateral pedal edema.  Laboratory values were serum creatinine concentration 11.16 mg/dL (his baseline creatinine was 1.0 mg/dL 3 weeks prior); blood urea nitrogen (BUN) 82 mg/dL; serum potassium 5.1 mEq/L; and serum bicarbonate (CO2) 19 mEq/L. A Foley catheter was placed. However, the patient remained anuric and dialysis was initiated.

Additional workup for acute kidney injury (AKI) was performed. Urine sediment showed many granular casts and numerous red blood cells (RBCs), a few of which were dysmorphic. His urine protein/creatinine ratio (PCR) was 2.92 g/g. The patient tested positive for anti-nuclear antibody (ANA), with a titer of 1:320 and anti-myeloperoxidase (MPO) antibody with a titer of 394.5 U/mL. Proteinase 3 (PR3) and glomerular basement membrane (GBM) autoantibodies were negative.

Complement levels were within normal range. Anti-histone antibody was weakly positive (1.2 U). Values less than 1.0 U are negative. The workup for bacterial and viral infections were unrevealing. Chest and abdomen CT scans demonstrated bronchovascular thickening, airway fluid, and ground glass opacity involving the right lung with small bilateral pleural effusion and mild bibasilar interstitial pulmonary edema. Kidneys appeared normal in size and texture without hydronephrosis.

A kidney biopsy was performed and results were consistent with diffuse, severely active MPO/ANCA-associated glomerulonephritis (GN) with all the glomeruli affected by active necrotizing cellular crescents (Figure 1). There was also concurrent IgG dominant immune complex deposition scattered in the mesangial and segmental capillary walls, and, to a less extent, in the subendothelial space. There was no significant mesangial or endocapillary hypercellularity. The patient was treated with pulse steroids (methylprednisolone 1000 mg infusion daily for 3 days) and rituximab infusions.

Figure 1. Cellular crescent in one of the glomeruli (silver stain). 
Loading Quiz...