Mixed connective tissue disease
Description
- Overlap syndrome defined serologically: high-titre anti-U1-RNP with features of SLE + systemic sclerosis + inflammatory myopathy (and often RA)
- *The antibody defines the disease - MCTD cannot be diagnosed without high-titre anti-U1-RNP*
The defining clinical quartet
- Raynaud phenomenon - the commonest and usually the first feature
- Puffy, swollen ("sausage") hands and fingers
- Arthritis - disproportionately severe for the other features, often RA-like and can be erosive
- Myositis - proximal weakness, raised CK
What is characteristically ABSENT
- Severe renal disease (mild membranous nephropathy occurs; diffuse proliferative lupus nephritis does not)
- Severe CNS disease (trigeminal neuropathy and aseptic meningitis do occur)
- Persistent high-titre anti-dsDNA and anti-Sm
- *Absence of these is what makes it MCTD rather than SLE*
Overlap vs undifferentiated
- Undifferentiated CTD (UCTD) - autoimmune features not meeting criteria for any single disease; ~1/3 evolve into a defined CTD within 5 years
- MCTD - a specific serologically defined entity, not the same thing
6 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access