10. Drug-induced lupus as a trigger for macrophage activation syndrome

INTRODUCTION: Macrophage activation syndrome (MAS) or haemophagocytic lympohistiocytosis (HLH) is a rare, life threatening cause of fever. It can be due to a primary haematological condition, but can also be triggered by several rheumatological conditions such as Stills disease or systemic lupus erythematosus. It can often be misdiagnosed as infection, leading to a delayed or even missed diagnosis. Given its life threatening course, we need not only recognise the syndrome, but also identify the underlying trigger so that appropriate treatment of the underlying cause can be initiated early. This case is the first reported case of drug-induced lupus causing MAS. CASE DESCRIPTION: This is a 56-year-old female of Indian origin who initially presented to rheumatology in January 2018 with a seronegative inflammatory arthritis. ANA was negative at this time and she had no other clinical features of a connective tissue disease. She was intolerant of methotrexate, so switched to sulphasalazine in October 2018. Unfortunately, sulphasalazine failed to control her disease, and she was assessed for biologic therapy in March 2019. It was noted she had travelled to India at the start of 2019, but IGRA screening in March returned negative prior to being considered for biologics. She was admitted to Daisy Hill Hospital in Newry, Northern Ireland on 22/3/19 with pyrexia, right sided abdominal pain and leucopenia. She was treated with several courses of broad spectrum antibiotics, but multiple blood and urine cultures came back negative. CT chest, abdomen and pelvis found duodenitis, but failed to identify a source of sepsis or evidence of tuberculosis. Echocardiogram was normal. Investigations from infectious diseases ruled out HIV, Hepatitis B&C, EBV, CMV, stongyloides, leishmaniasis, syphilis and malaria. Daily pyrexia persisted, and she developed a progressive pancytopenia, rash, mucositis and a rising ferritin up to 30000. Skin biopsy was non-specific but showed weak staining for IgM and C3 raising the possibility of vasculitis but was not definitive. Triglycerides were elevated at 3.6 and fibrinogen 1.2. ANA, which had initially been normal before sulphasalazine, was now positive at 1in40 with an anti-chromatin of 3.5 and ds-DNA 18. Complement was normal. CD25 soluble receptor later returned at 5370. Anti histone antibody was negative. Bone marrow biopsy confirmed MAS. She was treated with intravenous immunoglobulins, intravenous methylprednisolone for 3 days followed by prednisolone, and anakinra. Her fevers subsequently settled, ferritin normalised and her blood counts gradually improved. She was commenced on hydroxychloroquine and prednisolone dose weaned. DISCUSSION: Our working diagnosis in this case was that of a drug-induced lupus secondary to sulphasalazine therapy which then was complicated by MAS. This is the first reported case in the literature of a drug-induced lupus-driven MAS. We had considered if this could have represented a systemic lupus erythematosus picture from the onset of the inflammatory arthritis, however, the initial ANA was normal and only became positive after treatment with sulphasalazine. Interestingly, this patient’s ANA profile became negative following treatment with steroid/anakinra and following withdrawal of the drug. It is unusual that complement would be normal if this was a presentation of systemic lupus, and whilst anti histone antibody negativity perhaps points away from drug induced lupus, it can be negative in 5% cases of drug induced lupus. KEY LEARNING POINTS: Early recognition of MAS is imperative if we are to improve morbidity and mortality from this condition. It is important to be aware of potential triggers of the syndrome, and this case has highlighted a previously unrecorded cause of MAS in drug induced lupus. In this case, treatment with high dose steroid, intravenous immunoglobulin and anakinra, as well as withdrawing the causative drug, proved to be very effective in resolving her MAS. CONFLICT OF INTEREST: The authors declare no conflicts of interest.