Delayed diagnosis of adult onset Still's disease in 2 cases: diagnostic dilemma in positive antinuclear antibody and tuberculosis endemic areas.

Adult-onset Still's disease (AoSD) is a rare systemic autoinflammatory disorder of unknown etiology that affects young adults. Here, we report two cases of delayed AoSD diagnosis, which was initially diagnosed as tuberculous arthritis and systemic lupus erythematosus (SLE) before referral. In the first case, tuberculous arthritis treatment was commenced based on positive interferon-gamma release assay results, whereas in the second case, SLE was diagnosed based on clinical symptoms and positive antinuclear antibody results. There was no clinical improvement after treatment based on the initial diagnosis, patient referral, or diagnostic elaboration. After further evaluation, the clinical and laboratory features were found to be appropriate for the diagnosis of AoSD. Both patients had anemia, fever, arthritis, and high ferritin levels and were treated with high-dose methylprednisolone followed by methotrexate; clinical improvement was observed, and the ferritin levels reduced.