Mixed connective tissue disease
Mixed connective tissue disease (MCTD) is a type of connective tissue disease. With regards to clinical and imaging features, it can have significant overlap with other connective tissue diseases such as systemic lupus erythematosus and scleroderma 1. It is therefore classified as a type of overlap syndrome and at times it even comes under debate as to whether MCTD should exist as a distinct entity 7.
Mixed connective tissue disease is a rare autoimmune condition and is often defined by the presence of a ribonuclease-sensitive extractable nuclear antigen.
A prerequisite for the diagnosis of mixed connective tissue disease is the presence in the serum of high titres of antibodies against uridine-rich RNA-small nuclear ribonucleoprotein (snRNP) - anti-U1-RNP antibodies 10.
The presence of anti-U1-70 kd is considered a characteristic feature.
MCTD can affect various organ systems, with pulmonary 6 and musculoskeletal 4-5 being two of the key systems affected. As such these are best discussed under separate headings:
- pulmonary manifestations of mixed connective tissue disease
- musculoskeletal manifestations of mixed connective tissue disease
History and etymology
It was thought to have been first described by Gordon C Sharp and colleagues in 1972.
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- 9. Magro CM, Crowson AN, Regauer S. Mixed connective tissue disease. A clinical, histologic, and immunofluorescence study of eight cases. Am J Dermatopathol. 1997;19 (3): 206-13. Am J Dermatopathol (link) - Pubmed citation
- 10. Prakash UB. Respiratory complications in mixed connective tissue disease. Clin. Chest Med. 1999;19 (4): 733-46, ix. Pubmed citation