Mixed connective tissue disease (MCTD)

Mixed connective tissue disease (MCTD, Sharp's syndrome) is a rare, heterogeneous, multi-system autoimmune disorder. It is a distinct clinical entity, but features of systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and myositis may all be present. It is associated with anti-U1 ribonucleoprotein (RNP) antibodies.* It is not to be confused with 'undifferentiated connective tissue disease'.**

Epidemiology

• Male:female ratio 1:3
• Average age of presentation 30-40, may present in children
• Rare - incidence in adult population is estimated to be 2.1/million/year in one Norwegian study

Presentation:

• **Raynaud's** phenomenon often precedes other symptoms and occurs in 90% of cases
• Polyarthralgia/arthritis
• Myalgia
• 'Sausage fingers'(dactylitis)

Other clinically important features:

• Dermatological: photosensitive rash, scleroderma-like changes, alopecia
• Oesophageal dysfunction
• Respiratory: pleuritis, pulmonary hypertension, interstitial lung disease
• Haematological: anaemia, lymphadenopathy, splenomegaly, rarely TTP
• Cardiac: pericarditis, pericardial effusion, accelerated coronary artery disease
• Renal: glomerulonephritis (tends to be milder than SLE)
• Neuropsychiatric: seizures, mood disturbance

Investigations: