A 54-year-old female presents to the hospital because of hemoptysis. She has coughed up approximately 1 teaspoon of blood for the last 4 days. She has a history of cigarette smoking. A chest radiogram shows diffuse bilateral infiltrates predominantly in the lower lobes. The hematocrit is 30%, and the serum creatinine is 4.0 mg/dL. Both were normal previously. Urinalysis shows 2+ protein and red blood cell casts.
The presence of autoantibodies directed against which of the following is most likely to yield a definitive diagnosis?
A. Glomerular basement membrane
B. Glutamic acid decarboxylase
C. Phospholipids
D. Smooth muscle
E. U1 ribonucleoprotein (RNP)
The answer is A.
A variety of autoimmune diseases may cause pulmonary/renal disease, including Wegener’s granulomatosis, microscopic polyangiitis, SLE, and cryoglobulinemia. Goodpasture’s syndrome is characterized by the presence of anti–glomerular basement antibodies that cause glomerulonephritis with concurrent diffuse alveolar hemorrhage. The disease typically presents in patients over 40 years old with a history of cigarette smoking. These patients usually do not have fevers or joint symptoms. Among the listed options, antibodies to glutamic acid decarboxylase are seen in patients with type 1 diabetes or stiff-man syndrome, anti–smooth muscle antibodies in patients with autoimmune hepatitis, and anti–U1 RNP in those with mixed connective tissue disease. Antiphospholipid antibody syndrome may cause renal disease and alveolar hemorrhage, but this usually occurs in the context of a systemic illness with prominent thrombosis in other organ systems [extremities, central nervous system (CNS)].
A114141
The presence of autoantibodies directed against which of the following is most likely to yield a definitive diagnosis?
A. Glomerular basement membrane
B. Glutamic acid decarboxylase
C. Phospholipids
D. Smooth muscle
E. U1 ribonucleoprotein (RNP)
The answer is A.
A variety of autoimmune diseases may cause pulmonary/renal disease, including Wegener’s granulomatosis, microscopic polyangiitis, SLE, and cryoglobulinemia. Goodpasture’s syndrome is characterized by the presence of anti–glomerular basement antibodies that cause glomerulonephritis with concurrent diffuse alveolar hemorrhage. The disease typically presents in patients over 40 years old with a history of cigarette smoking. These patients usually do not have fevers or joint symptoms. Among the listed options, antibodies to glutamic acid decarboxylase are seen in patients with type 1 diabetes or stiff-man syndrome, anti–smooth muscle antibodies in patients with autoimmune hepatitis, and anti–U1 RNP in those with mixed connective tissue disease. Antiphospholipid antibody syndrome may cause renal disease and alveolar hemorrhage, but this usually occurs in the context of a systemic illness with prominent thrombosis in other organ systems [extremities, central nervous system (CNS)].
A114141
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