A 29-year-old woman has Raynaud phenomenon, puffy fingers, inflammatory polyarthritis, and dysphagia. She also reports myalgia with proximal weakness and CK of 1,900 U/L. ANA shows a speckled pattern at high titre. Which single antibody result would best unify these findings?

• A High titre anti-U1 RNP ✓
• B Anti-Jo-1
• C Anti-topoisomerase I (Scl-70)
• D Anti-Mi-2

Explanation

Mixed connective tissue disease is defined by overlapping features of scleroderma, polymyositis, and lupus together with very high titre anti-U1 RNP antibodies, classically producing a speckled ANA pattern. Anti-Jo-1 marks antisynthetase syndrome with mechanic hands and interstitial lung disease but does not explain the overlap phenotype. Anti-Scl-70 defines diffuse scleroderma with interstitial fibrosis, and anti-Mi-2 marks dermatomyositis, neither of which accounts for the combined lupus-like and myositis features.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.