Antiglomerular basement membrane disease with normal renal function.
CASE PRESENTATION A 23-year-old man was referred to Peking University First Hospital with a 4-month history of intermittent hemoptysis. One month before admission, he experienced severe hemoptysis with cough and respiratory distress. His hemoglobin was 71.0 g/l, urinalysis revealed protein 1 +, and red blood cells 3-5/high-power field (HPF). Arterial blood gas analysis showed pH 7.385, PO 2 58 mm Hg, PCO 2 40 mm Hg, and SaO 2 88%. Chest radiograph showed diffusely parenchymal shadows in both lungs. He was diagnosed as having a pulmonary infection with respiratory failure type I and was treated with ceftazidime and erythromycin, but no improvement was obtained after 3 weeks. One week before admission, an antiglomerular basement membrane (GBM) antibody was detected positive by enzyme-linked immunosorbent assay (ELISA) using purified bovine α(IV)NC1 as solid-phase antigen. He was then referred to our hospital. The patient was a car repairman with a 5-year exposure to gasoline and diesel. He smoked 1-2 packs of cigarettes per day for 4 years. Physical examination revealed a well-nourished man with no edema or rash. The temperature was 36.8°C, blood pressure 130/85 mm Hg, and pulse 90/min. The heart rate and rhythm was regular. Moist rales could be heard in both lungs. The abdomen was soft and non-tender without organomegaly. Laboratory data on admission were as follows: white blood cells 12.8 x 10 9 /l (normal range, 3.5-9.5 x 10 9 /l), hemoglobin 62.0g/l (137-179g/l), platelet 178 x 10 9 /l (100-300 x 10 9 /l). Hepatic function was normal. Serum creatinine was 94.0/μmol/l (44-133 μmol/l) and blood urea nitrogen was 6.3 mmol/l (1.8-7.1 mmol/l). Electrolytes were in the normal range. Serum albumin was 39.6 g/l (35-50 g/l). Urinalysis revealed red blood cells 3-5/HPF (0-3/HPF) and dysmorphic red cells and the 24-h urine protein was 0.87g (<0.15g/24h). Erythrocyte sedimentation rate was 14 mm/1 h (<15mm/1 h). C-reactive protein, rheumatoid factor, antineutrophil cytoplasmic antibodies, and antinuclear antibodies were all negative. Anti-GBM antibodies were positive at 23% tested by ELISA as described above (normal range, <13%), with a titer of 1:400. Although there was a broad differential, including small vessel vasculitis, systemic lupus erythematosus, pulmonary infection, tuberculosis, and heart failure, the clinical presentation and the laboratory workup were most compatible with a diagnosis of anti-GBM disease with Goodpasture's syndrome. After admission, a renal biopsy was performed.