Rheumatology Question 37 Instructor

Often when a patient has a positive ANA (anti-nuclear antibody) an ENA (extractable nuclear antibody) panel is also requested. Certain profiles of these antibodies are associated with particular patterns of disease.

What tests are included in an ENA panel, and with what diseases do they correspond?

The ENA panel commonly includes antibodies to Smith antigen (Sm), SS-A (Ro), SS-B (La), topoisomerase I (Scl-70), ribonuclear protein (RNP), tRNA-synthetase (Jo-1), and centromere.

Anti-Sm antibodies are very specific for SLE, but only occur in 25-30% of patients. Anti-Ro and anti-La antibodies are associated with Sjogren’s syndrome (seen in 70% and 60% of patients, respectively), SLE (30% and 15%), subacute cutaneous lupus and neonatoal lupus.

Anti-Scl-70 antibody is associated with diffuse scleroderma.

Anti-centromere antibody is associated with limited scleroderma (CREST).

Anti-RNP antibody is associated with mixed connective tissue disease.

Anti-Jo-1 antibodies are associated with dermatomyositis.

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