Section: USMLE

41) A 57-year-old woman with a history of hypertension and arthritis is referred to a rheumatologist for evaluation. A complete blood count (CBC) is normal, and a mini-chem panel shows no electrolyte abnormalities. Her erythrocyte sedimentation rate (ESR) is elevated, and an antinuclear antibody test (ANA) is positive. Further antibody studies are performed, and the results are shown below.

Anti-histones	high titer
Anti-double stranded DNA	not detected
Anti-single stranded DNA	not detected
Anti-SSA	not detected
Anti-SSB	not detected
Anti-SCI-70	not detected
Anti-Smith	not detected
Anti-centromere	not detected
Anti-RNP	not detected

Which of the following diseases is suggested by these results?

1. CREST syndrome
2. Diffuse form of scleroderma
3. Drug-induced lupus
4. Sjögren syndrome
5. Systemic lupus erythematosus (SLE)

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 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, 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 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 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).