Mixed Connective Tissue Disease — SCE Rheumatology MCQ

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ModerateConnective Tissue DiseaseMixed Connective Tissue DiseaseSCE Rheumatology

A 45-year-old woman presents with symmetrical polyarthritis, Raynaud phenomenon and puffy hands. ANA is positive at a titre of 1:1280 and anti-U1 RNP is strongly positive. Anti-dsDNA, anti-Sm and anti-Scl-70 antibodies are negative. She also has mild proximal muscle weakness with a creatine kinase concentration of 450 U/L. Mixed connective tissue disease is diagnosed. What is the leading disease-related cause of death in this condition?

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Correct answer: D — Pulmonary arterial hypertension

The correct answer is **E, pulmonary arterial hypertension (PAH)**. Raynaud phenomenon, puffy hands, inflammatory polyarthritis, myositis and high-titre anti-U1 RNP support MCTD. PAH is its leading disease-related cause of death and may develop independently of extensive interstitial lung disease. Severe immune-complex nephritis is less characteristic of MCTD than of SLE, making renal failure an uncommon cause of death. Infection contributes to mortality, particularly during immunosuppressive treatment, but has not exceeded PAH in directly studied MCTD cohorts. Malignancy and cardiovascular or cerebrovascular events can occur but are not the characteristic leading disease-related cause. The original key is therefore correct, but the question and teaching material have been refined to specify disease-related mortality and remove unsupported screening and treatment assertions.

Reference: Hajas A, et al. Clinical course, prognosis, and causes of death in mixed connective tissue disease. Journal of Rheumatology. 2013;40:1134-1142. https://pubmed.ncbi.nlm.nih.gov/23637328/