Delayed Diagnosis: Adult-Onset Still's Disease Initially Mistaken for Tuberculosis in a Nigerian Man.

Adult-onset Still's disease (AOSD) is a rare autoimmune disorder characterised by fever, rash, joint pain, and elevated ferritin levels. It is extremely difficult to diagnose due to its overlap with other autoimmune and infective causes. If left untreated, systemic inflammation can rarely trigger an exaggerated immune response, leading to secondary haemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (a secondary subtype of HLH). This case demonstrates AOSD complicated by HLH in a Nigerian man in his 30s with fever, shortness of breath, night sweats, and joint pain, where the working diagnosis for weeks of admission was tuberculosis. Investigations suggested a lymphadenopathic infection; however, poor response to broad-spectrum therapies and repeated negative cultures eventually led to the consideration of AOSD. This patient developed high ferritin levels, pancytopenia, hypofibrinogenaemia, and hypertriglyceridaemia with both liver and kidney failure. This patient was taken to critical care with renal and liver dysfunction. He improved with aggressive steroid therapy and was discharged from hospital.