120 Serious erythroderma occurring in an anti-SAE-1 positive dermatomyositis (DM) patient

Abstract

Background: The idiopathic inflammatory myopathies (IIM) are autoimmune inflammatory diseases characterised by muscle weakness and potential for skin inflammation (DM). Myositis-specific autoantibodies (MSA) are increasingly used to diagnose IIM patients, clearly correlating with IIM subgroup specific phenotype features2. Anti-small ubiquitin-like modifier-1 activating enzyme (SAE) is a DMspecific MSA3. We report an anti-SAE-1 positive DM patient whose disease course was complicated by serious erythroderma, resistant to multiple standard DMARDs and eventually responding to rituximab. Methods: This 51-year-old female singer was referred by dermatology to the Salford Adult Myositis Clinic with an eight month history of disturbed singing capability, myalgia and florid DM rash, more recently with associated with weakness. Referring investigations included a CK level over 400U/L, MRI scans of thighs demonstrating minimal vastus medialis myoedema, and electromyography consistent with a myopathy. Serology by line-blot 4 screening (Eurimmun) demonstrated that she was anti-SAE-1 antibody positive. At rheumatology review, she was on prednisolone 40mg daily, with improvement of myalgia. However, examination revealed a very florid DM rash with classic Gottron's papules and heliotrope rash but with severe subcutaneous oedema over both thighs. Lower limb muscle testing was normal, but the deltoids appeared weak (4+/5). The therapeutic plan was to commence DMARDs with further investigations arranged. Percutaneous muscle biopsy confirmed mild perifascicular changes. Intense cancer-orientated investigations all proved negative. Results: She was established on methotrexate 20mg weekly, but developed worsening rash and further painful ulcerating skin lesions. She thus received a five-day course of intravenous immunoglobulins but with no obvious beneficial response. She therefore received a single bolus of IV cyclophosphamide (10m/kg) but her dermal status continued to deteriorate and she developed whole body erythroderma with rigors. She was admitted urgently to hospital admission for pulsed IV methylprednisolone (1 gram daily for three days). She required antibiotics for confirmed secondary staphylococcal skin infection. Repeat MR of thighs revealed patchy vastus medialis myositis, but with very obvious fasciitis. Her CK remained normal throughout this hospital stay. The patient improved with antibiotics and was discharged to receive rituximab. This has improved both skin and muscle symptoms, and it has been possible to implement a planned reduction of corticosteroid therapy. She is currently well with regard to her muscles and on a reducing dose of prednisolone. Her singing voice has apparently returned to normal although she has not gone back on the road yet. Conclusion: This case illustrates the complexity of diagnosing and managing IIMs. Erythroderma is a rare but potentially life-threatening complication of DM, and in such cases prompt diagnosis, aggressive treatment and close liaison with dermatology teams are imperative. This case also highlights the need for vigilance when assessing such patients as CK values can be normal in the presence of covert myositis.