Rheumatology
Mixed Connective Tissue Disease
혼합결체조직병
Overlap of SLE, SSc, PM features + high-titer anti-U1 RNP
- How common
- Uncommon
- Typical age
- 20s–30s (9:1 female)
What is it?
Anti-U1 RNP autoimmunity drives overlapping SLE, SSc, and polymyositis features.
Commonly affected: Joints, skin, muscle, lung, esophagus
How it develops
- Anti-U1 RNP formationHigh-titer anti-U1 RNP autoantibody
- B-cell activationIL-6-mediated B-cell hyperactivity
- Multi-organ involvementMixed SLE+SSc+PM manifestations
- PAH progressionLeading cause of mortality
Symptoms
- Pulmonary hypertensionLeading cause of death
- Raynaud phenomenonNearly universal, often first symptom
- MyositisProximal weakness
- Puffy handsCharacteristic edematous hands
- ArthritisRA-like polyarthritis
How it is examined
- High-titer anti-U1 RNPRequired for diagnosis; anti-Sm negative
- Alarcón-Segovia criteriaSerology + clinical (≥3 features)
- Echo (PAH screening)Regular monitoring for PAH
Imaging
Non-erosive joint X-rays; assess lungs for ILD.
- Non-erosive joints
- Possible ILD
HRCT for ILD; echo for PAH.
- NSIP pattern
- PA dilation
Non-surgical care
- HydroxychloroquineFoundation for joint/skin symptoms
- NSAIDsMild arthralgia
- Low-dose corticosteroidsFor active disease
- Raynaud managementCCBs, warmth
- PAH monitoringRegular echocardiography
Conservative options are generally tried first. Medications listed here can have side effects — discuss them with your prescriber.
When surgery is considered
Severe organ involvement
Procedures that may be discussed
- High-dose steroids + MMF (myositis, ILD)
- Cyclophosphamide (severe ILD)
- Rituximab
- PAH-targeted therapy (bosentan, sildenafil)
Outlook
Better than SLE/SSc; 10-year survival 80%. PAH is leading cause of death.