Mixed connective tissue disease
The annual incidence of MCTD is estimated to be 1.9 per 100 000 population. MCTD is more common in females than males (5:1) and presents most commonly in the second and third decades of life.
The sequential appearance of symptoms makes diagnosis challenging, but the basic hallmarks include elevated antinuclear antibodies (ANA), hand / joint findings such as Raynaud phenomenon and swelling, and nonspecific symptoms including fever, fatigue, and myalgias. MCTD has a wide-ranging clinical presentation, from minimally symptomatic to life-threatening cardiac, kidney, or pulmonary involvement. Evolution to other connective diseases is infrequent. MCTD has been associated with HLA-DR4 and HLA-DR2.
Pulmonary hypertension is the most serious complication (occurring in up to 25% of patients) and a major cause of death in MCTD.
M35.1 – Other overlap syndromes
398049005 – Mixed collagen vascular disease
Differential Diagnosis & Pitfalls
- Rheumatoid arthritis
- Dermatomyositis / polymyositis
- Systemic lupus erythematosus (SLE) – The absence of hypocomplementemia or anti-dsDNA and anti-Sm antibodies helps to distinguish MCTD from SLE.
- Limited cutaneous scleroderma / CREST syndrome
- Systemic sclerosis – Diffuse involvement of the face, upper trunk, or extremities observed in patients with systemic sclerosis is usually not seen in MCTD. More severe arthritis and myositis help distinguish MCTD from systemic sclerosis.
- Sjögren syndrome