SAT0600 Multicentric reticulohistiocytosis (1980–2017): clinical correlates, treatment outcomes & association with autoimmunity & malignancy

Background Multicentric reticulohistiocytosis (MRH) is a rare systemic disease characterised by papulo-nodular skin eruptions and a rapidly progressive, deforming arthritis. It can mimic rheumatic disorders such as rheumatoid arthritis or dermatomyositis. Immunosuppression is often helpful, but challenging due to the association of MRH with malignancy. Objectives To examine the clinical correlates and outcomes of MRH and its association with malignancy and other autoimmune conditions Methods A retrospective review of all patients with MRH treated at our institution between 01/01/1980 and 04/30/2017 was performed. Demographics, clinical features, laboratory tests, imaging findings, histopathology, treatments and outcomes were abstracted. Data on autoimmune disorders and malignancies before and after MRH diagnosis were collected. Results We identified 24 patients with MRH(58% female,75% Caucasian,mean age at diagnosis 52 y). Median length of follow up was 2.3 y. All patients had confirmed diagnosis by histopathology(23 skin, 7 synovial). All patients had cutaneous and articular involvement. Nodular skin lesions were noted in 96% patients(periungual area and dorsal hand in 87%, periarticular 61%[around DIP 42%,PIP 25%,MCP 8%], face 54%, arms 42%, back 29%, neck 21%, legs 21%, ears 12%, scalp 12%). Mucosal nodules were noted in 30%. Regarding articular involvement, 22 (92%) had arthralgia, 21 (88%) patients had joint swelling, and 13 (54%) had synovitis. Frequency of joint involvement was upper extremity PIP(29%)>upper extremity DIPs, MCPs, wrist >MTPs, Toes >Knees > Elbows. Radiographic erosions were noted in 67% patients. Constitutional symptoms included fatigue(,15 unintentional weight loss(,10 lymphadenopathy(4 and pruritis(.11 Systemic features included dysphagia(,5 photosensitivity(,4 dry eyes(,3 pericarditis(2 and pleuritis(.1 Several patients had positive autoimmune serologies: ANA(,8 RF(,5 Anti-CCP(,3 SS-A(,3 SS-B(,2 Anti-DsDNA(.1 A third of patients had concomitant autoimmune disorders: inflammatory arthritis(,3 Sjogrens(,1 chronic focal granulomatous nephritis(,1 JRA(,1 psoriasis(,1 myasthenia gravis and ITP(.1 A third of patients(8/24) had malignancy:malignant melanoma(,3 basal cell carcinoma(,2 and 1 each with ovarian carcinoma, squamous cell carcinoma lung, peritoneal adenocarcinoma, and endometrial carcinoma. Most patients were treated with systemic glucocorticoids(15 and oral DMARDs(13: methotrexate(,8 cyclophosphamide(,10 chlorambucil(2 and cyclosporine(.1 Biologics were used in 4 patients(1 infliximab,2 etanercept,1 adalimumab). Only 2 patients had complete resolution of their symptoms, while majority showed only partial improvement. 10 (44%) patients developed joint deformities involving: wrist(,4 MCP(,4 PIP(,7 DIP(,4 knee(2 and MTP(.3 None had arthritis mutilans. 75% patients were alive at last follow up. Conclusions To our knowledge, this is the largest series of MRH patients from a single institution, highlighting the rarity of the condition, and an unmet need for treatment options that can allow sustained disease remission. We emphasise the need for histopathology to distinguish it from mimicking rheumatic conditions and initiating early aggressive treatment to potentially prevent deforming joint disease. A high vigilance for malignancy and other autoimmune diseases is necessary. Disclosure of Interest None declared