Undifferentiated rheumatic diseases and overlap syndromes

Name	Synonyms
Mixed connective tissue disease
Lupus-scleroderma-polymyositis-rheumatoid arthritis
Undifferentiated systemic rheumatic disease	(Early) undifferentiated connective tissue, collagen vascular, or autoimmune disease
Nonclassic systemic lupus erythematosus	Lupus-like, lupus variant, or near, borderline, latent, incipient, incomplete, possible, or probable lupus^[1,2]
Nonclassic rheumatoid arthritis	Palindromic rheumatism^[3], pre-rheumatoid arthritis, early rheumatoid arthritis
Nonclassic scleroderma	Prescleroderma^[4]
Overlap syndromes
Rheumatoid arthritis-lupus	Rhupus
Scleroderma-polymyositis/dermatomyositis
Scleroderma-lupus
Scleroderma-rheumatoid arthritis
Other scleroderma overlaps
Polymyositis overlaps
Juvenile idiopathic arthritis-lupus
Sjögren's syndrome overlaps
Other
Undifferentiated polyarthritis syndrome
Undifferentiated spondyloarthritis

References:

Greer JM, Panush RS. Incomplete lupus erythematosus. Arch Intern Med 1989; 149:2473.
Lambers WM, Westra J, Jonkman MF, et al. Incomplete lupus erythematosus: What remains after application of the American College of Rheumatology and systemic lupus international collaborating clinics criteria? Arthritis Care Res 2020; 72:607.
Ellingwood I, Schieir O, Valois MF, et al. Palindromic rheumatism frequently precedes early rheumatoid arthritis. Results from an incident cohort. ACR Open Rheumatology 2019; 1:614.
Valentini G, Pope JE. Undifferentiated connective tissue disease at risk for systemic sclerosis: Which patients might be labeled prescleroderma? Autoimmunity Rev 2020; 19:102659.

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