[Eosinophilic fasciitis: From pathophysiology to therapeutics]. / Fasciite à éosinophiles : actualités physiopathologiques et nouvelles voies thérapeutiques.

Eosinophilic fasciitis (EF) is a rare connective tissue disorder characterized by painful edema and induration of the limbs and trunk, likely associated with hypereosinophilia and hypergammaglobulinemia. EF causes arthralgia and range of motion limitation, leading to significant functional impairment and poor quality of life. Since its description by Shulman in 1974, over 300 cases have been reported. We present here a review of the latest diagnostic, pathophysiological and therapeutic developments in this disease. Magnetic resonance imaging appears useful to guide diagnosis and biopsy. Diagnosis is based on a deep skin biopsy involving the fascia, which will reveal edema, sclerofibrosis of the muscular fascia and subcutaneous tissue, and an inflammatory infiltrate sometimes composed of eosinophilic polynuclear cells. EF may occur in patients treated with immune checkpoint inhibitors and the diagnosis should be raised in case of cutaneous sclerosis in these patients. The pathophysiology of the disease remains poorly understood, and its management lacks randomized, controlled, blinded trials. First-line treatment consists in oral corticosteroid therapy, sometimes combined with an immunosuppressant, mainly methotrexate. A better understanding of the pathophysiology has opened new therapeutic perspectives and clarified the role of targeted therapies in the management of EF, such as interleukin-6 inhibitors, whose efficacy has been reported in several cases.

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.