A 38-year-old woman presents with proximal muscle weakness, heliotrope rash over the eyelids, Gottron papules over the MCP and PIP joints, and mechanic's hands. CK is 3200 U/L. Anti-Jo-1 antibody is positive. HRCT chest shows basilar-predominant ground-glass opacities with reticulation. What is the most likely diagnosis?
- A Immune-mediated necrotizing myopathy
- B Anti-synthetase syndrome ✓
- C Dermatomyositis (anti-MDA5 positive)
- D Polymyositis
Correct answer: B. Anti-synthetase syndrome
Explanation
Anti-synthetase syndrome is characterized by the triad of inflammatory myopathy, interstitial lung disease, and anti-aminoacyl-tRNA synthetase antibodies (most commonly anti-Jo-1). Other features include mechanic's hands, Raynaud phenomenon, and arthritis. Anti-MDA5 dermatomyositis causes rapidly progressive ILD with minimal myopathy. Necrotizing myopathy typically has very high CK and anti-SRP or anti-HMGCR antibodies. Polymyositis lacks skin findings.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.