USMLE Answer 41

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41. The correct answer is C. The single finding of high autoantibody titers to histones, without any other autoantibodies, is characteristic of drug-induced lupus. The most commonly implicated drugs are procainamide, hydralazine (given for hypertension), and isoniazid. Patients typically have milder disease than in systemic lupus erythematosus (SLE) and tend to have arthritis, pleuropericardial involvement, and, less commonly, rash. CNS and renal disease are not usually observed.

CREST syndrome (choice A) is a milder variant of scleroderma characterized by calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia. Anti-centromere antibodies are diagnostic.

The diffuse form of scleroderma (choice B), also known as systemic sclerosis, causes fibrosis of the skin and internal viscera. This disorder is characterized by anti-SCI-70 and often low titers of many other autoantibodies.

Sjögren syndrome (choice D) is characterized by dry eyes and dry mouth. Sjögren syndrome in isolation is characteristically positive for anti-SS-A and anti-SS-B. If it accompanies rheumatoid arthritis, anti-RNP will be positive as well.

SLE (choice E) is a multisystem disorder that is distinguished from drug-induced lupus by the presence of a wide variety of autoantibodies, including anti-double stranded DNA (Anti dsDNA).