Antisynthetase syndrome — SCE Rheumatology MCQ

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EasyConnective tissue diseasesAntisynthetase syndromeSCE Rheumatology

A 51-year-old woman has a 3-month history of progressive proximal muscle weakness, myalgia and breathlessness. Examination shows mechanic's hands, reduced proximal muscle power and bilateral basal inspiratory crackles. Her creatine kinase is 4100 IU/L, anti-Jo-1 antibodies are positive, and HRCT of the chest shows an organising-pneumonia pattern of interstitial lung disease. What is the most likely diagnosis?

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Correct answer: D — Antisynthetase syndrome

The diagnosis is **antisynthetase syndrome**. Anti-Jo-1 is an anti-aminoacyl-tRNA synthetase antibody, and its combination with inflammatory proximal myopathy (weakness and markedly elevated CK), mechanic's hands and interstitial lung disease is highly characteristic. Organising pneumonia is a recognised pattern of myositis-associated ILD. Polymyalgia rheumatica causes shoulder and hip girdle pain and stiffness but not objective muscle weakness, a CK of 4100 IU/L or anti-Jo-1 positivity. Inclusion body myositis typically causes slowly progressive quadriceps and finger-flexor weakness, often asymmetrically, and does not cause this serological-pulmonary phenotype. Sarcoidosis can affect muscle and lung but does not account for anti-Jo-1 with mechanic's hands. SLE-associated myositis would require supportive lupus clinical or immunological features.

Reference: Cavagna L, et al. Clinical manifestations and treatment of antisynthetase syndrome. Current Treatment Options in Rheumatology. 2020. https://pubmed.ncbi.nlm.nih.gov/32284267/