Mixed connective tissue disease — SCE Rheumatology MCQ

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EasyConnective tissue diseasesMixed connective tissue diseaseSCE Rheumatology

A 35-year-old woman has Raynaud phenomenon, puffy swollen fingers and arthralgia. Examination shows mild synovitis but no sclerodactyly or other skin thickening. Oesophageal manometry confirms dysmotility. Investigations show a high-titre speckled ANA and strongly positive anti-U1 RNP antibodies. What is the most likely diagnosis?

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Correct answer: B — Mixed connective tissue disease

The diagnosis is mixed connective tissue disease. The discriminating combination is strongly positive, high-titre anti-U1 RNP antibodies with Raynaud phenomenon, puffy hands, inflammatory synovitis and oesophageal dysmotility. These represent overlapping connective-tissue-disease manifestations typical of MCTD. Limited systemic sclerosis can cause Raynaud phenomenon and oesophageal dysmotility, but the absence of skin thickening and the anti-U1 RNP-dominant inflammatory phenotype favour MCTD. Anti-U1 RNP antibodies may occur in SLE, but the stem lacks characteristic SLE manifestations or SLE-specific serology. Rheumatoid arthritis does not explain the Raynaud–puffy-hand–oesophageal phenotype. Undifferentiated connective tissue disease is less appropriate because the clinical and serological pattern supports a recognised MCTD phenotype. Pulmonary arterial hypertension and interstitial lung disease are important subsequent complications.

Reference: Ferrara CA et al. Towards Early Diagnosis of Mixed Connective Tissue Disease: Updated Perspectives. ImmunoTargets and Therapy. 2023;12:79–89. https://pubmed.ncbi.nlm.nih.gov/37525698/