Abstract Background/Aims Adult-onset Still’s disease (AOSD) is a rare auto-inflammatory condition characterised by a daily fever, polyarthritis and salmon-pink rash. It is commonly associated with a markedly raised ferritin and can be complicated by secondary haemophagocytic lymphohistiocytosis (HLH). This case discusses the difficulties of differentiating between uncontrolled inflammation and infection especially in an immunosuppressed patient. Methods A 35-year-old man presented with a 10-day history of daily fevers, pharyngitis, myalgia and polyarthritis. He was originally from Nigeria and moved to the UK in 2022 before relocating to Northern Ireland in February 2025. He was previously healthy and had no response to oral antibiotic treatment in the community. Initial bloods revealed a normocytic anaemia (Hb 79g/L) with a significantly elevated ferritin (23,933 µg/L). He had deranged liver function along with an elevated CRP (186 mg/L) and ESR (140 mm/hr). Bone marrow aspirate demonstrated haemophagocytic activity and a H-score was calculated at 197 (80-88% probability of HLH). Results He was commenced on IV methylprednisolone followed by oral prednisolone and anakinra. This led to a resolution of his fever and a significant reduction in his ferritin. Despite this improvement he discharged himself against medical advice. He represented later with a recurrence of his hyperferritinaemia (50,506 µg/L) along with a severe hepatitis (ALT 2700 U/L, AST 1600 U/L, bilirubin 106 µmol/L). A liver biopsy showed severe necrotising hepatitis with haemosiderosis. He was discussed at the HLH MDT and it was felt that this hyperinflammatory state was more in keeping with AOSD rather than primary HLH. His fevers continued and he became confused and blood cultures grew Listeria monocytogenes. A lumbar puncture confirmed bacterial meningitis. His GCS deteriorated and he was intubated ventilated and admitted to intensive care. Antibiotics were commenced and he responded well allowing him to be extubated 48 hours later. His immunosuppression (anakinra) was decreased to allow a balance between immunosuppression and managing infection. Ferritin and liver function tests improved only after antimicrobial therapy which suggests that the Listeria infection may have driven his relapsed hyperinflammatory state. He was discharged on tapering prednisolone and anakinra and at 1-month follow-up remained well with ferritin 1,000 µg/L and normalised liver function. Conclusion This case demonstrates the diagnostic challenge of differentiating between AOSD and infection. Interestingly this patient only improved following treatment for Listeria monocytogenes rather than escalating immunosuppression. We know that immunosuppressive therapy predisposes to opportunistic infections. Therefore, prompt recognition of infection is essential in immunosuppressed patients with a high inflammatory state. Disclosure M. Donnelly: None. S. Black: None.
Donnelly et al. (Wed,) studied this question.