American Board of Internal Medicine (ABIM) Certification Practice Exam

Which of the following features is NOT associated with Mixed Connective Tissue Disease?

1. Raynaud phenomenon

2. Skin thickening

3. Dermatomyositis

4. Myositis

The correct answer is: Dermatomyositis

Mixed Connective Tissue Disease (MCTD) is characterized by overlapping features of several autoimmune conditions, particularly systemic lupus erythematosus, systemic sclerosis, and polymyositis. Among the listed features, dermatomyositis, which involves muscle weakness and a distinctive skin rash, is not typically associated with MCTD. Raynaud phenomenon, skin thickening, and myositis are frequently seen in MCTD. Raynaud phenomenon, characterized by episodic vasospasm of the fingers and toes, is common because it is associated with vascular involvement found in several connective tissue diseases. Skin thickening can result from sclerodermatous changes that are also common in cases of MCTD, reflecting the overlap with systemic sclerosis. Myositis, or inflammation of muscle, is observed as part of the polymyositis symptoms that can present in MCTD patients. Dermatomyositis is a distinct entity, specifically involving muscle inflammation and unique skin manifestations, making it less relevant in the context of MCTD, and therefore, identifying dermatomyositis as not associated helps differentiate between these interconnected but distinct disorders.