A 28-year-old man has had hemoptysis and hematuria for the past 2 days. On physical examination, his temperature is 36.8deg C, pulse is 87/min, respirations are 19/min, and blood pressure is 150/90 mm Hg. Laboratory studies show creatinine of 3.8 mg/dL and urea nitrogen of 35 mg/dL. Urinalysis shows 4+ hematuria, 2 + proteinuria, and no glucose. A renal biopsy specimen examined microscopically shows glomerular damage and linear immunofluorescence with labeled complement C3 and anti-IgG antibody. Which of the following autoantibodies has the greatest specificity for this patient's condition?
Anti-basement membrane
Anticardiolipin
Anti-double-stranded DNA
Anti-histone
He has Goodpasture syndrome, in which an autoantibody is directed against type IV collagen in basement membranes of the glomeruli and in the lung. This is a form of type II hypersensitivity reaction. The antibodies attach to the basement membrane and fix complement, damaging the glomeruli. Anticardiolipin, along with anti-b2 -glycoprotein "lupus anticoagulant," are found with antiphospholipid syndrome, which may appear in systemic lupus erythematosus (SLE). These patients have coagulopathies with thrombosis or bleeding, or both. Anti-double-stranded DNA antibodies have specificity for SLE, whereas anti-histone antibodies are characteristic of drug-induced SLE. Anti-SS-A antibody is seen in Sjogren syndrome. The anti-Ul-ribonucleoprotein antibody is seen in mixed connective tissue disease (MCTD).
Immunity