Chapter 30: Anti-Glomerular Basement Membrane Disease (Goodpasture Disease)
A 54-year-old Caucasian woman is admitted with severe hypoxemia and a serum creatinine of 3.9 mg/dL (6 weeks previously it had been 1.9 mg/dL). She had a fever of 38°C and there were small patches of palpable purpura on both arms. There were no signs of fluid overload, her BP was 140/85 mm Hg but she had widespread crackles in both lungs. Urine was dipstick positive for protein (++) and blood (+++) and contained an active urinary sediment with red blood cell casts.
Which one of the following tests is most likely to be positive?
A. Urinary antigen test or PCR for Legionella spp
B. Immunoassay for circulating anti-GBM antibodies
C. Blood cultures for Streptococcus pneumoniae
E. Toxicological screen for paraquat
The answer is D. The patient has combined renal and respiratory failure—or pulmonary renal syndrome—which has many causes. These can be segregated into six broad groups: immune mediated; directly caused by infection; fluid overload caused by acute tubular necrosis; left heart failure with pulmonary oedema and renal hypoperfusion; direct toxicity from paraquat; and rarely caused by an assortment of other conditions. Usually the critical distinction is between immune-mediated and infection-mediated disease. None of the diagnoses is excluded by the information given in the clinical vignette but the rate of rise serum creatinine together with urinary dipstick results and active urine sediment make acute tubular necrosis or tubulointerstitial disease extremely unlikely which makes answers A, C, and E wrong. Instead, they strongly suggest glomerulonephritis with a rapidly progressive clinical course of which anti-GBM disease or ANCA-associated vasculitis (AAV) with pauci-immune focal necrotizing glomerulonephritis are the most likely. Both cause severe crescentic glomerulonephritis but the rate of deterioration of renal function is more typical of AAV since the evolution of anti-GBM disease is usually more explosive. More decisively, palpable purpura indicative of leukocytoclastic vasculitis is not a feature of anti-GBM disease but occurs commonly in AAV. Accordingly answer B is wrong and answer D is correct. The facts favor a diagnosis of pauci-immune focal necrotizing glomerulonephritis caused by AAV and positive ANCA. Given the findings the ANCA is most likely to be specific for myeloperoxidase and the clinical diagnosis to be microscopic polyangiitis.
A 48-year-old Caucasian woman was referred because of incidentally discovered dipstick positive proteinuria (+++) and hematuria (++). She was hypertensive (150/95) but otherwise the physical examination was normal. Serum creatinine was 1.8 mg/dL and proteinuria 4.8 g/24 hours. Kidney biopsy revealed membranoproliferative glomerulonephritis on light microscopy and intense linear deposition of IgG along the GBM was seen on immunofluorescence; no immune deposits were visible on ...