Case presentation
An 81-year-old female patient with a 5-year history of microscopic hematuria presented to our institution in May 2017 with complaints of gross hematuria and fatigue persisting for 2 months, and nausea and anorexia persisting for 10 days, but with no fever, edema, oliguria, weight loss, or hemoptysis. She had a history of diabetes mellitus for 20 years and a history of hypertension for 9 years.
Physical examination revealed blood pressure (BP) at 120/80 mmHg, normal sinus rhythm, moderate anemic appearance, and moist rales in her left lower lung. Laboratory results indicated rapidly progressive deterioration of renal function. Serum creatinine (SCr) was 97.6 μmol/L on February 21, 254.2 μmol/L on April 28, and 276.1 μmol/L on May 2, 2017 (range: 41–111 μmol/L). Urinalysis showed 3+ blood, 2+ protein, and full-visual-field red blood cells (RBCs) per high-power field with 60% dysmorphic RBCs. Serum albumin was 38.4 g/L, and 24-hour urinary protein quantitation was 4.26 g. Hemoglobin (Hb) was 76 g/L, the white blood cell count (WBC) was 7.54 × 109/L, platelet count (PLT) was 177 × 109/L, and erythrocyte sedimentation rate (ESR) was 69 mm/h (range: 0–15 mm/h). The concentrations of plasma C3 (54.1 mg/dl) and C4 (1.56 mg/dl) were significantly reduced (range: 90–180 mg/dl and 10–40 mg/dl, respectively). Anti-double-stranded deoxyribonucleic acid (anti-dsDNA), anti-Smith (anti-Sm), anti-Sjogren syndrome A antibody (anti-SSA), and anti-Sjogren syndrome B (anti-SSB) antibodies were all negative with weakly positive antinuclear antibody (1:160). Test results for rheumatoid factor, C-reactive protein (CRP), and serum cryoglobulin were normal. ANCA enzyme immunoassay revealed a perinuclear staining pattern (p-ANCA) and serum anti-myeloperoxidase (MPO) antibody of 119 units/ml (normal: < 20 U/ml), whereas anti-protease 3 and serum anti-glomerular basement membrane antibody concentrations were normal. The results of infectious studies for hepatitis C (HCV), hepatitis B (HBV), and human immunodeficiency virus (HIV) were negative. Renal ultrasonography showed normally-sized kidneys and increased cortical echogenicity. Chest computed tomography (CT) indicated a small nodule in the superior lobe of the right lung and a ground-glass opacity nodule in the superior lobe of the left lung (Fig. 1).
We diagnosed AAV; renal biopsy was not performed because the patient declined this procedure.