FRI0448 Mda5 antibody positive clinical amyopathic dermatomyositis (CADM): a single tertiary centre case series of 13 patients
Authors: K. Huang, K. Shojania, J. Yeung, A. Avina-Zubieta
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Positive anti-melanoma differentiation-associated gene 5 (MDA5) antibody has been reported in 50%–73% of patients with clinical amyopathic dermatomyositis (CADM)<sup>1</sup>. About half of MDA5 +CADM patients die of rapid progressive interstitial lung disease (RP-ILD), defined as worsening dyspnea within 1 month that required high-flow oxygen therapy or ventilator support in previously stable patients. <h3>Objectives</h3> This descriptive study aims to systematically characterise the clinical features, treatment and outcome of 13 cases of MDA5 +CADM patients at a single referral centre. <h3>Methods</h3> Myositis antibody testing became available at Vancouver Coastal Health, Canada since 2014. We retrospectively reviewed clinical presentations, laboratories, imaging studies, treatment and outcome of patients with MDA5 antibody. The data is presented descriptively. <h3>Results</h3> Total 13 cases (4 male and 9 female) of MDA5 +CADM were identified (2014–2017). Mean age was 49.9±11.5. Ten were Asian descent (8 Chinese, 1 Philippine, and 1 Indo-Mauritian) and 3 Caucasians. All 13 patients had typical DM rash (heliotrope, Gottron's, mechanic's hands, periungual erythema). Cutaneous ulcers over the extensor surfaces of joints were seen in 7/13 and palmar papules in 4/13, both of which were characteristic for MDA5 +CADM. Only 3/13 patients had CK elevation with little muscle weakness; all others had normal CK and no detectable weakness. ILD was present in all 13 patients. 7/13 (53.8%) patients had RP-ILD and 4/13 (30.7%) died within 3 months of onset of worsening dyspnea, despite steroid, cyclophosphamide, Rituximab, cyclosporine and IVIG; 3 survived after receiving lung transplant. 6/13 (46.2%) patients had stable ILD and are still alive. 5/7 patients with RP-ILD (71.4%) had coexisting Ro52 antibody whereas only 1/6 patients with stable ILD (16.7%) had Ro52. Of the 6 patients with stable ILD, one had worsening cutaneous ulceration and ILD that required IV cyclophosphamide; one had refractory dermatitis and recurrent pneumomediastinum eventually stabilised on rituximab; one responded to tacrolimus with improving respiratory symptoms; one had panniculitis refractory to IVIg, hydroxychloroquine, azathioprine and tofacitinib, and ultimately responded to IV cyclophosphamide; one had mild ILD but severe cutaneous disease who eventually agreed to rituximab, and the last patient went with traditional Chinese medicine and lost follow up. None had underlying malignancy. <h3>Conclusions</h3> In this case series of 13 patients with MDA5 +CADM, 54% were Chinese, a finding similar to previous reported higher incidence in Asians. It is important to recognise the characteristic cutaneous and pulmonary features of this entity early on as mortality is high. Refractory panniculitis can be found in MDA5 +CADM. All patients had ILD with 54% RP-ILD and 31% mortality within 3 months. Coexisting Ro52 may be predictive of worse prognosis. Early intensive immunosuppression is instrumental for refractory cutaneous manifestation and/or progressive ILD. As lung transplantation became more available, three patients with RP-ILD in this series received lung transplant successfully and they were maintained on mycophenolate and tacrolimus after transplant. <h3>Reference</h3> [1] Sato S, et al. Autoantibodies to a 140-kd polypeptide, CADM-140, in Japanse patients with clinically amyopathic dermatomyositis. Arthritis Rheum2005;52:1571–6. <h3>Disclosure of Interest</h3> None declared