Definition
Mixed connective tissue disease (MTCD) is an unusual systemic inflammatory rheumatic disease. MCTD could be a specific subset of the wider category of rheumatic “overlap syndromes”, a term used to describe when a patient has features of over than one classic inflammatory rheumatic disease. These classic rheumatic diseases consist of systemic lupus erythematosus, polymyositis, scleroderma, and rheumatoid arthritis.
• Routine tests:
o CBC
o ESR
o CRP
o Routine blood chemistry
o Urinalysis
• Immunology tests
• Autoantibodies:
o ANA
o RNP- Positive in 95-100% MCTD patients
o dsDNA, Sm, Ribosomal-P- present in MCTD patients
• Other tests:
o Immunoglobulins- hypergammaglobulinemia
o Rheumatoid factor- often positive
o Anti-CCP- often positive
Algorithm
References:
1. Sharp GC, Irvin WS, Tan EM, et al. Mixed connective tissue disease–an apparently distinct rheumatic disease syndrome associated with a specific antibody to an Extractable Nuclear Antigen (ENA). Am J Med 1972; 52:148–59.
2. Brouwers MC, Kho ME, Browman GP, et al. AGREE II: advancing guideline development, reporting and evaluation in health care. Can Med Assoc J 2010;182: E839–42.
3. Benito-Garcia E, Schur PH, Lahita R, et al. Guidelines for immunologic laboratory testing in the rheumatic diseases: anti-Sm and anti-RNP antibody tests. Arthritis Rheum 2004; 51:1030–44.
