Objective: To evaluate the clinical features and causes of misdiagnosis of anti-Jo-1 syndrome.
Methods: The data of 33 polymyositis (PM)/dermatomyositis (DM) patients with anti-Jo-1 antibody hospitalized from January 1997 to June 2002 in Peking Union Medical College Hospital were reviewed retrospectively. The initial symptom, clinical and laboratory characteristics, diagnosis, efficacy of therapy and follow-up were studied.
Results: 51.5% of the patients developed lung impairment and 24.2% of the patients developed arthritis/arthralgia before the onset of PM/DM, only 5 patients had the typical rash, and/or myalgia and muscle weakness as the initial symptoms (15.2%). Patients with anti-Jo-1 syndrome were usually misdiagnosed as with rheumatoid arthritis (27.3%), idiopathic pulmonary fibrosis (12.1%), and pneumonia (15.2%). Anti-Jo-1 syndrome was associated with inflammatory myositis (100%), interstitial lung disease (ILD) (93.9%), fever (60.6%), polyarthritis/polyarthralgia (54.5%), Raynaud's phenomenon (21.2%), and sclerodactyly (21.2%). The muscle symptom was relatively mild and the symptom of ILD was relatively severe. Treatment of corticosteroid plus immunosuppressive drugs was effective in achieving initial remission, while relapse was frequent.
Conclusion: Few patients with anti-Jo-1 syndrome have the episode of classical myositis as initial symptom. Lung impairment, especially ILD, and joint involvement are more common in early phase of the disease.