LAUSR

Erdheim-Chester disease is a rare non-Langerhans cell histiocytosis with multiorgan involvement. Otherwise known as polyostotic sclerosing histiocytosis it is characterised by proliferation and infiltration of lipid laden macrophages into bone marrow. Extraskeletal involvement is commonly seen involving heart, CNS, skin, lung, kidney, and retroperitoneum resulting in a variety of presenting features. Case: 75-year-old male referred to rheumatology connective tissue disease clinic by respiratory team with dyspnoea and unintentional weight loss of 20kg in one year. CT had shown pleural effusions and interstitial markings in mid zones felt to be due to cardiac failure. PMH - IHD, CABG. Mildly elevated dsDNA of 10. He denied cough, sputum or haemoptysis. No mouth ulceration, alopecia, sicca symptoms, Raynaud's, rashes, fevers, myalgia, or joint swelling. No family history of rheumatic disease. On examination reduced air entry to lung bases, no synovitis, no nail bed changes, no lymphadenopathy. Further investigations showed persistent mildly elevated dsDNA, crithidia negative, negative ANA on HEp2, Hb 136, WCC 13.8, PLT 329, complement levels normal, Igs normal, IgG4 normal, NTproBNP raised 3196, ESR 27, CRP 28. Further CT CAP - bilateral pleural effusions, thickened enhancement of pleura bilaterally without focal mass, increased interstitial markings lung mid zones, significant thick pericardial enhancement and pericardial effusion, thickening around distal oesophagus and a rind of inflammatory thickening around distal thoracic aorta. Transthoracic echocardiogram - small pericardial effusion without haemodynamic compromise, normal left and right ventricular function. NM whole body - marked increased uptake in diametaphyseal regions of tibial bones and distal aspect of femora. MRI femurs - significant symmetrical abnormality in distal femoral shaft and metaphyseal region of both femora, endosteitis with extensive linear and patchy reduction T1 signal intensity and increase in STIR intensity within medullary cavity of distal femur. CT guided biopsy of distal femur identified foamy histiocytic infiltration with fibrosis. BRAF mutation testing of plasma showed strong positive result confirming molecular diagnosis of Erdheim-Chester disease. Cardiac MRI had been requested and MRI of brain was normal. He was treated initially with 40mg prednisolone, weaned to 15mg, and weekly PEG interferon with improvement in dyspnoea and weight loss. However, he deteriorated slowly over the next year and died of cardiac failure. Histiocytic disorders such as Erdheim-Chester disease do rarely present to rheumatology given multisystem involvement and diagnostic uncertainty. This patient had skeletal, cardiac, lung, and gastrointestinal involvement resulting in his dyspnoea and weight loss. Initial treatment involves corticosteroid and interferon. Approximately 50% of patients have BRAF mutation and may respond to vemurafenib therapy. Our patient unfortunately deteriorated prior to being considered for this treatment. Prognosis is poor with a 3-year survival of 50%. Disclosure G. Starritt: None. D. McCormick: None.