ABSTRACT
Miopatía Necrotizante Autoinmune (MNA) fue reconocida como nuevo sub-grupo de miositis luego de observar en biopsias musculares la presencia de necro-sis con escaso o ausente infiltrado inflamatorio, sumado a la expresión de dos an-ticuerpos específicos de miositis (Anticuerpo anti Partícula de Reconocimiento de Señal, anti-SRP; y Anticuerpo anti Hidroxi-3-metilglutaril-CoA reductasa, anti-HM-GCR), ambos fuertemente asociados al hallazgo histológico descrito y a fenotipos clínicos característicos a cada anticuerpo, los cuales comparten importantes simi-litudes representadas por severa debilidad muscular proximal, gran elevación de creatinkinasa (CK), escasa manifestación de síntomas y signos extramusculares, y resistencia al uso de inmunosupresión habitual. Si bien en primera instancia los criterios de clasificación propuestos estaban basados en la histología, la obser-vación de necrosis en otros subgrupos de miositis, sumado a la homogeneidad del comportamiento clínico de pacientes que expresaban anticuerpos anti-SRP o anti-HMGCR independiente de la histología presentada, llevó en el año 2016 al Grupo de Trabajo del Centro Europeo Neuromuscular (ENMC) a establecer crite-rios diagnósticos de MNA basados en el comportamiento clínico (debilidad mus-cular proximal con CK total elevada) más la presencia del anticuerpo respectivo (anti-SRP o anti-HMGCR), reservando la necesidad de realizar biopsia muscular en el caso que la serología resulte negativa, siendo así reconocidas tres entidades distintas de MNA: Miopatía anti-SRP, Miopatía anti-HMGCR y Miopatía Necroti-zante seronegativa. La presente revisión expresa el actual conocimiento de MNA y sus subtipos, refiriéndose a aspectos históricos, clínicos, histológicos, inmuno-patológicos, y de pronóstico y tratamiento.
Necrotizing autoinmune myopathy (NAM) was recognized as a new sub-group of myositis after the observation of necrosis with mild or absent inflam-matory infiltrates in muscle biopsies, in addition of expression of two specific myositis antibodies (antiSRP and antiHMGCR), which are strongly associated to the mentioned hystologic findings, with different clinical phenotypes depending on the presence of each antibody, but sharing some features like severe proximal muscle weakness, significant elevation of creatin phosphokinase (CK), mild ex-tramuscular involvement and resistance to commonly used immunosupressants. The first proposed approach to classification criteria was hystology-based, none-theless the observation of necrosis in some other types of myositis and the homo-geneity of clinical features in patients expressing antiSRP or antiHMGCR despite the hystologic findings led to a new classification scheme leaded by the European Neuromuscular Center in 2016, which recognizes thre different clinical entities of NAM, based on the antibody expression plus the presence of proximal muscle weakness, relying hystology to a secondary place thus eliminating the need for immediate biopsy to stablish a diagnosis: those are antiSRP myopathy, antiHMG-CR myopathy and seronegative necrotizing myopathy, being the last one the only needing muscle biopsy. The present review shows the actual knowledge about NAM and its subtypes, referring to hystoric, clinical, hystologic, immunopatholog-ic, prognostic and therapeutic issues.
Subject(s)
Humans , Autoimmune Diseases/pathology , Myositis/pathology , Autoimmune Diseases/immunology , Muscular Diseases , Myositis/diagnosis , Myositis/physiopathology , Myositis/therapy , Myositis/epidemiology , Necrosis/immunology , Necrosis/pathologyABSTRACT
Objective To characterize the clinical,electrophysiology and neuropathological features of 4 cases with immune-mediated necrotizing myopathy (IMNM).Methods We retrospectively analyzed the clinical,electrophysiology,neuropathological characteristics of 4 IMNM patients with muscular and skin biopsy in our department during 4 years (from January 2011 to January 2014).Results Among these 4 patients,2 were men and 2 were women (aged 37 to 58 years) with disease duration ranging from 1 month to 60 months.Two patients were with acute onset and 2 with chronic onset.All 4 patients had proximal muscle weakness with three patients with cervical flexor muscle weakness and one with respiratory muscles weakness and noninvasive ventilator assisted respiration.One patient had interstitial lung disease.The anti-signal recognition particle antibodies were strong positive in all 4 patients.Muscle biopsy showed group necrotizing and regenerating fibers in one patient and few scattered necrotizing and regenerating fibers in the other 3 patients.Both muscle fiber hypertrophy and muscle fiber atrophy together with proliferation of connective tissue on endomysium could be viewed in all 4 patients.However,very few inflammatory cells were detectable in patients.One patient was treated with corticosteroids and the other three were treated with combination of corticosteroids and immunosuppressant drugs.Conclusions IMNM is characterized by heterogeneity at disease onset,severity and ilnvolvement of muscles with,however,similary pathological changes including the presence of numerous necrotic and regenerating fibers with little or none inflammation.Corticosteroid and/or immunosuppressant is effective for patients.