Review Question - QID 100456

The patient's presentation is consistent with systemic lupus erythematosus (SLE). Anti-dsDNA and Anti-Smith antibodies have the greatest specificity, 95% and 99% respectively, for diagnosing SLE.

SLE is a connective tissue disease that affects vasculature, joints, skin, and kidneys. It occurs most commonly in women of childbearing age. The clinical manifestations of SLE are highly variable and include: malar rash, glomerulonephritis, pleuritis, pericarditis, photosensitivity, arthralgias, and more.

Gill et al. review the use of anti-dsDNA antibodies in the diagnosis of SLE. In order to make the diagnosis, 4 of 11 clinical and laboratory criteria must be met. The primary laboratory test is an antinuclear antibody titer, however given the low prevalence of SLE in the general population, the antinuclear antibody titer has a relatively low predictive value in asymptomatic individuals. The American College of Rheumatology recommends obtaining a titer only in individuals present with characteristic symptoms of at least two organ systems.

Munoz et al. discuss the role of anti-dsDNA antibodies in the pathogenesis of SLE. Anti-dsDNA is highly specific for SLE and can be found in 95% of individuals with active, untreated disease. The authors posit that biologic and pathogenic properties of Anti-dsDNA is directly responsible for some of the organ damage seen in SLE patients.

Figure A depicts a malar rash in the characteristic butterfly pattern seen in SLE patients. Illustration A depicts an algorithm for diagnosing SLE.

Incorrect answers:
Answer 1: Anti-ACh receptor antibodies are seen in myasthenia gravis.
Answer 2: Anti-Ro (Anti-SS-A) antibodies are most specific for Sjogren's syndrome (70-95%) and have a 25-50% specificity for SLE.
Answer 3: Anti-La (Anti-SS-B) antibodies have a 60-90% sensitivity for Sjogren's syndrome.
Answer 4: Anti-ssDNA antibodies are not used to diagnose SLE.