Overview
Definition
An overlap syndrome sharing clinical features of systemic lupus erythematosus, systemic sclerosis, and polymyositis, in the presence of high titers of anti-U1 RNP antibodies.
Epidemiology
Affects females in >90% of cases, typical onset in young to middle age.
Etiology & Risk Factors
- Autoimmune inflammation and immune complex deposition with high specificity for U1 RNP
Clinical Symptoms
- Raynaud's phenomenon (almost universal)
- Swollen, puffy hands ('sausage fingers')
- Arthritis / Artralgias
- Myositis (muscle weakness and pain)
- Sclerodactyly
Clinical Approach
Diagnosis
- High titer of serum Anti-U1 RNP antibodies
- Absence of other specific autoantibodies (like anti-dsDNA or anti-Scl-70)
- Elevated inflammatory markers
Management
- Corticosteroids (highly responsive)
- NSAIDS and hydroxychloroquine for mild joint symptoms
- Vasodilators for Raynaud's
Complications
- Pulmonary hypertension (most common cause of death)
- Interstitual lung disease
- Glomerulonephritis (rare)