Sammendrag

• Refers to a group of conditions that have clinical features of, and meet classification criteria for, more than 1 well-characterised rheumatic disease.
• The spectrum of overlap syndromes includes mixed connective tissue disease (MCTD); antisynthetase syndrome; and polymyositis/scleroderma (PM/Scl) overlap syndrome.
• MCTD is a distinct clinical entity characterised by overlapping features of systemic lupus erythematosus (SLE), scleroderma, myositis, and rheumatoid arthritis in the setting of a high titre of auto-antibodies to U1-ribonucleoprotein.
• Antisynthetase syndromes form a distinct group characterised by antibodies directed against various aminoacyl-tRNA synthetase enzymes with overlapping clinical features of myositis, arthritis, and interstitial lung disease.
• PM/Scl syndrome is characterised by overlapping features of scleroderma and polymyositis, PM/Scl antibody, Raynaud's phenomenon (RP), tendon inflammation, and interstitial lung disease.
• Treatment of overlap syndromes is tailored to the active clinical manifestations and ranges from supportive therapy to cytotoxic immunosuppressive regimens.