E001 Recurrent haemophagocytic lymphohistiocytosis (HLH) secondary to adult-onset Still’s Disease (AOSD): a diagnostic challenge

Background/Aims Haemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome caused by uncontrolled activation of cytotoxic T cells and macrophages, leading to excessive cytokine production. Secondary HLH is often associated with infection, malignancy or autoimmune diseases. We present a case of a young woman with recurrent HLH features triggered by an underlying adult-onset Still’s disease (AOSD). Methods A 48-year-old Afro-Caribbean woman first presented in 2017 with pyrexia, rashes, arthralgia, pruritus, hyperferritinaemia (>40,000 µg/L), transaminitis, and raised inflammatory markers. She underwent excessive work up for pyrexia of unknown origin but no obvious cause was found. Her liver biopsy revealed iron-laden Kupffer cells (>60%), suggestive of haemolysis, and HFE mutation testing was negative. Her symptoms self-resolved after a couple of months with normalisation of ferritin, and she was discharged from gastroenterology follow-up. This episode was attributed to sepsis and she underwent interval cholecystectomy. Results Four years later she presented again with very similar symptoms and investigations showed mild haemolytic anaemia, thrombocytopenia, raised CRP (85), transaminitis, and hyperferritinemia (36,770 µg/L), low haptoglobin, elevated LDH (1647 IU/L). She was empirically treated for infection, but during extensive infectious screening both viral and bacterial tests were normal. No evidence of malarial parasite was noted. Rheumatology input led to further workup for HLH and investigations showed raised triglycerides (4.9 mmol/L), and soluble CD25 (5,688 U/mL). Bone marrow biopsy confirmed hemophagocytes. Genetic testing excluded primary HLH. Malignancy was excluded after a PET-CT and the lymph node biopsy showed only reactive changes. She was started on high doses of steroids for HLH and became symptomatically better within a few days. The steroids were tapered and stopped after few months. She remained symptom free without the need for any long term immunosuppression. She had two more recurrences after one year with very similar symptoms, albeit mild in intensity and followed the typical pattern of fever, arthralgia, fatigue, rash, itching and high ferritin over 6000. Each of these episodes improved with another course of oral steroids with a slow wean over 6 weeks. Patient declined long-term immunosuppressive treatments. Conclusion Both AOSD and secondary HLH are hyperferritinemic cytokine storm disorders that present with overlapping features. In our case, recurrent HLH is likely to be triggered by an underlying autoimmune process such as AOSD, as the patient meets the Yamaguchi criteria. Early recognition of these overlapping syndromes is crucial and investigations - including sCD25 levels and monitoring steadily rising ferritin - can assist in differentiating patients at risk of progression to HLH. Disclosure W. Mushtaq: None. S. Honarius: None. A. Onajole: None. D. Makkuni: None.