Related Subjects:
|Relapsing Polychondritis
|Reactive Arthritis
|Raynaud's Phenomenon
|Polymyositis
|Dermatomyositis
|Polyarteritis nodosa
|Osteoporosis
|Rheumatoid Arthritis
|Systemic Sclerosis (Scleroderma)
|Rheumatology Autoantibodies
|Overlap Syndrome
|Sjögren’s syndrome
|Mixed Connective Tissue Disease (MCTD)
|Anti-RNP Antibody
📖 About Mixed Connective Tissue Disease (MCTD)
- A rare systemic autoimmune rheumatic disease showing overlapping features of:
- Systemic Lupus Erythematosus (SLE)
- Scleroderma
- Polymyositis
- Rheumatoid Arthritis (RA)
- Sometimes described as an “overlap syndrome”.
🧬 Aetiology
- Strongly associated with anti-U1 ribonucleoprotein (RNP) antibodies → present in ~95–100% of cases.
- Other antibodies: anti-Sm (occasionally), rheumatoid factor (~50%).
- Exact pathogenesis: immune dysregulation with production of autoantibodies that target nuclear proteins → systemic inflammation.
🩺 Clinical Features
- Joint & Muscle:
- Arthralgia/arthritis (RA-like)
- Myositis → proximal muscle weakness
- “Sausage-like” puffy hands/fingers
- Skin & Vascular:
- Raynaud’s phenomenon – often first manifestation
- Sclerodermatous skin changes in some patients
- GI & Respiratory:
- ↓ Oesophageal motility → dysphagia, reflux
- ↓ Pulmonary diffusion capacity → dyspnoea
- Risk of pulmonary arterial hypertension (major prognostic factor)
- Other systemic features: Can mimic SLE (rash, serositis), or overlap with RA (erosive arthritis).
🔬 Investigations
- Serology:
- Anti-U1 RNP antibodies – diagnostic hallmark
- Anti-Sm antigen (sometimes positive)
- Rheumatoid factor in ~50%
- Other labs: ANA+, raised ESR/CRP, cytopenias.
- Functional tests: Pulmonary function (↓ DLCO), echocardiography (screen PAH).
💊 Management
- Symptomatic relief:
- NSAIDs for arthritis
- PPIs/antacids for reflux
- Calcium-channel blockers (e.g., nifedipine) or losartan for Raynaud’s
- Disease-modifying drugs:
- Low-dose corticosteroids + hydroxychloroquine (first-line)
- Methotrexate / azathioprine for arthritis or myositis
- Cyclophosphamide for severe organ involvement
- Biologics (TNF inhibitors, rituximab) in refractory disease
- Monitoring: Pulmonary hypertension surveillance with echocardiography ± right heart catheterisation.
📈 Prognosis
- Highly variable – depends on organ involvement.
- 10-year survival ~30–80% (worst in cases with pulmonary hypertension or renal crisis).
- Better prognosis than classic SLE or diffuse scleroderma, but risk of morbidity from chronic arthritis, PAH, or interstitial lung disease.
📚 Reference
