Diagnostic potential of sarcoplasmic myxovirus resistance protein A expression in subsets of dermatomyositis.

AIMS: To elucidate the diagnostic value of sarcoplasmic expression of myxovirus resistance protein A (MxA) for dermatomyositis (DM) specifically analysing different DM subforms, and to test the superiority of MxA to other markers. METHODS: Immunohistochemistry for MxA and retinoic acid-inducible gene I (RIG-I) was performed on skeletal muscle samples and compared with the item presence of perifascicular atrophy (PFA) in 57 DM patients with anti-Mi-2 (n = 6), -transcription intermediary factor 1 gamma (n = 10), -nuclear matrix protein 2 (n = 13), -melanoma differentiation-associated gene 5 (MDA5) (n = 10) or -small ubiquitin-like modifier activating enzyme (n = 1) autoantibodies and with no detectable autoantibody (n = 17). Among the patients, nine suffered from cancer and 22 were juvenile-onset type. Disease controls included antisynthetase syndrome (ASS)-associated myositis (n = 30), immune-mediated necrotizing myopathy (n = 9) and inclusion body myositis (n = 5). RESULTS: Sarcoplasmic MxA expression featured 77% sensitivity and 100% specificity for overall DM patients, while RIG-I staining and PFA reached respectively 14% and 59% sensitivity and 100% and 86% specificity. In any subset of DM, sarcoplasmic MxA expression showed higher sensitivity than RIG-I and PFA. Some anti-MDA5 antibody-positive DM samples distinctively showed a scattered staining pattern of MxA. No ASS samples had sarcoplasmic MxA expression even though six patients had DM skin rash. CONCLUSIONS: Sarcoplasmic MxA expression is more sensitive than PFA and RIG-I expression for a pathological diagnosis of DM, regardless of the autoantibody-related subgroup. In light of its high sensitivity and specificity, it may be considered a pathological hallmark of DM per se. Also, lack of MxA expression in ASS supports the idea that ASS is a distinct entity from DM.

Risk factors for treatment failure in scabies: a cohort study.

BACKGROUND: Treatment failure, which occurs in about one-third of cases, is considered as a major factor in the increasing incidence of scabies in developed countries. OBJECTIVES: To identify predictors of treatment failure of scabies in ambulatory populations. METHODS: This multicentre study compared the clinical characteristics and treatment modalities between a group of patients with scabies treated successfully and another group who were not cured 3 months after antiscabies treatment. RESULTS: In total 210 patients with a diagnosis of scabies were included, comprising 98 patients in the treatment success group and 112 in the treatment failure group. The main risk factors for treatment failure were (i) the use of only one type of treatment, topical benzyl benzoate (BB) or oral ivermectin, vs. the combination of both treatments [odds ratio (OR) 2·15, 95% confidence interval (CI) 1·22-3·77]; (ii) the use of a single intake (vs. two) of oral ivermectin (OR 10·2. 95% CI 4·49-23·2); (iii) intake of ivermectin during a meal vs. on an empty stomach (OR 4·31, 95% CI 1·89-9·84); (iv) absence of decontamination of furnishings (OR 8·72, 95% CI 3·50-21·8), in particular sofa and cushions (OR 5·90, 95% CI 2·34-14·9), mattresses (OR 4·16, 95% CI 1·35-12·8) or car seats (OR 6·57, 95% CI 3·27-13·2) and (v) absence of written documents explaining treatment modalities (OR 5·18, 95% CI 2·57-10·4). In multivariate analysis, treatment failure was mainly associated with (i) use of a single intake (vs. two) of ivermectin (OR 6·62, 95% CI 2·71-16·2); (ii) use of BB alone vs. two intakes of ivermectin (OR 3·51, 95% CI 1·55-7·95) and (iii) absence of decontamination of furniture with acaricides (OR 5·81, 95% CI 1·96-16·7). CONCLUSIONS: Use of topical BB alone and a single intake (vs. two) of ivermectin are predictors of treatment failure.

[Psoriatic arthritis during rituximab treatment of granulomatosis with polyangiitis: a new paradoxical side effect?]. / Rhumatisme psoriasique au cours d'un traitement par rituximab pour une polyangéïte avec granulomatose : une nouvelle réaction paradoxale ?

INTRODUCTION: Rituximab is a monoclonal antibody targeting the CD20 molecule of the B lymphocyte. Its efficacy has been recently reported in ANCA-associated vasculitis. We report a case of psoriatic arthritis that occurs during a treatment with rituximab in granulomatosis with polyangiitis. CASE REPORT: A 66-year-old woman, without past history of psoriasis, presented with a relapsing granulomatosis with polyangiitis in July 2010 with sinus and lung involvement. Treatment with rituximab was started, allowing a complete remission in 6 months. Two months after the first two infusions of rituximab she developed asymmetric arthritis of 3 distal interphalangeal joints. A few months later, the clinical presentation showed asymmetrical arthritis of the hands and wrists and dactylitis. Standard radiographs and MRI showed an inflammatory impairment according with psoriatic arthritis. CONCLUSION: Accountability of rituximab was retained in the development of the disease given the chronology of psoriatic arthritis development. It may be a paradoxical reaction, by analogy to those observed in anti-TNFα.