Dermatomyositis: Muscle Pathology According to Antibody Subtypes

Background and Objectives:Discoveries of dermatomyositis specific antibodies (DMSAs) in dermatomyositis patients raised awareness of various myopathological features among antibody subtypes. However, only perifascicular atrophy and perifascicular myxovirus resistant protein A (MxA) overexpression were officially included as the definitive pathological criteria for dermatomyositis classification. We aimed to demonstrate myopathological features in MxA-positive dermatomyositis to determine characteristic myopathological features in different DMSA subtypes.Method:We performed a retrospective pathology review of muscle biopsies of dermatomyositis patients diagnosed between January 2009 and December 2020 in a tertiary laboratory for muscle diseases. We included all muscle biopsies with sarcoplasmic expression for MxA and seropositivity for DMSAs. MxA-positive muscle biopsies which tested negative for all DMSAs were included as seronegative dermatomyositis. We evaluated histological features stratified according to four pathology domains (muscle fiber, inflammatory, vascular, and connective tissue) and histological features of interest by histochemistry, enzyme histochemistry, and immunohistochemical study commonly used in the diagnosis of inflammatory myopathy. We performed ultrastructural studies of 54 available specimens.Result:A total of 256 patients were included. Of these, 249 patients were positive for one of the five DMSAs (seropositive patients: 87 anti-TIF1-γ; 40 anti-Mi-2; 29 anti-MDA5; 83 anti-NXP-2; and 10 anti-SAE DM) and 7 patients were negative for all five DMSAs (seronegative patients). Characteristic myopathological features in each DMSA subtype were as follows: anti-TIF1-γ with vacuolated/punched out fibers (64.7%, P<.001) and perifascicular enhancement in HLA-ABC stain (75.9%, P<.001); anti-Mi-2 with prominent muscle fiber damage (score 4.8±2.1, P<.001), inflammatory cell infiltration (score 8.0±3.0, P=.002), perifascicular atrophy (67.5%, P=.02), perifascicular necrosis (52.5%, P<.001), increased perimysial alkaline phosphatase activity (70.0%, P<.001), central necrotic peripheral regenerating fibers (45.0%, P<.001), and sarcolemmal membrane attack complex deposition (67.5%, P<.001); anti-MDA5 with scattered/diffuse staining pattern of MxA (65.5%, P<.001) with less muscle pathology and inflammatory features; anti-NXP2 with microinfarction (26.5%, P<.001); and anti-SAE and seronegative DM with HLA-DR expression (50.0%, P=.02 and 57.1%, P=.02, respectively).Discussion:We described a comprehensive serological-pathological correlation of DM primarily using MxA expression as an inclusion criterion. In our study, DMSAs were associated with distinctive myopathological features suggesting different underlying pathobiological mechanisms in each subtype.

Dermatomyositis- Related Intestinal Dysmotility

Dermatomyositis (DM) is an inflammatory myopathy characterized by proximal muscle weakness and pathognomonic skin lesions. A 69-year-old woman with a recent diagnosis of DM one month prior, treated with corticosteroids and immunomodulators, presented to our inpatient rehabilitation with worsening dysphagia and constipation. At the time of our evaluation, physical examination was notable for erythematous papules over the MCPs, PIPs, elbows, and knees as well as a violaceous rash on the face. Muscle strength was diminished bilaterally with proximal distribution being affected greater than distal. Laboratory studies were notable for CK level 31 IU/ L, ANA by immunofluorescence of 1:80, and aldolase 4 u/L. The eleven-antibody myositis panel was negative. Skeletal muscle biopsy of the left thigh showed partially treated acquired inflammatory myopathy with perifascicular atrophy. During hospitalization, she was found to have pulmonary embolism. She received enoxaparin 1 mg/kg subcutaneous BID. Soon after, she developed rectal bleeding. Colonoscopy showed a stercoral ulcer caused by chronic constipation. While dysphagia is common, being present in 25-50% of patients with DM, lower gastrointestinal problems involving the small and large intestine are rare and typically present as a late manifestation of the disease. Decreased peristalsis in the large colon can lead to constipation, impaction, and subsequent mucosal ulceration, and pressure necrosis induced by fecaloma formation. Although rare, our case highlights the importance of recognizing gastrointestinal complications that dermatomyositis can cause and the effects that those complications have on morbidity and mortality.

Dermatomyositis: Muscle Pathology According to Antibody Subtypes

Importance: Current pathological criteria of dermatomyositis (DM) do not recognize different features among DM subtypes classified by dermatomyositis-specific antibodies (DMSAs). Objective: To determine whether myopathological features differ among DM subtypes classified by DMSAs and whether the pathological features can be characterized by serologically defined DM subtype. Design: Retrospective review of muscle pathology slides of 256 patients diagnosed with DM from January 2009 to December 2020. Setting: Single center study in a tertiary laboratory for muscle diseases. Participants: A total of 256 patients whose DM diagnosis was pathologically confirmed based on the sarcoplasmic expression of myxovirus resistant protein A (MxA) were included. Of these, 249 patients were positive for one of the 5 DMSAs (seropositive patients, anti-TIF1-γ=87, anti-Mi-2=40, anti-MDA5=29, anti-NXP-2=83, and anti-SAE=10), and 7 were negative for all 5 DMSAs (seronegative patients). Exposure: Histochemical, enzyme histochemical, immunohistochemical staining, and ultrastructural study. Main outcomes and measures: Histological features stratified according to four pathology domains: muscle fiber, inflammatory, vascular, and connective tissue domains, and histological features of interest by histochemistry, enzyme histochemistry, and immunohistochemical study commonly used in the diagnosis of inflammatory myopathy. Results: DMSAs significantly associated with characteristic histochemical and immunohistochemical features were as follows: anti-TIF1-γ with vacuolated/punched out fibers (64.7%, P<.001) and perifascicular enhancement in HLA-ABC (75.9%, P<.001); anti-Mi-2 with prominent muscle fiber damage (score 4.8±2.1, P<.001), inflammatory cell infiltration (score 8.0±3.0, P=.002), perifascicular atrophy (67.5%, P=.02), perifascicular necrosis (52.5%, P<.001), increased perimysium alkaline phosphatase activity (70.0%, P<.001), central necrotic peripheral regenerating fibers (45.0%, P<.001), and sarcolemmal deposition of the membrane attack complex (67.5%, P<.001); anti-MDA5 with scattered/diffuse staining pattern of MxA (65.5%, P<.001) with less muscle pathology and inflammatory features; and anti-NXP2 with microinfarction (26.5%, P<.001); and anti-SAE and seronegative DM with HLA-DR expression (50.0%, P=.02 and 57.1%, P=.02 respectively). Conclusion and relevance: We described an extensive study on serological-pathological correlation of DM primarily using MxA expression as an inclusion criterion. DMSAs was associated with distinctive myopathological features in our studied cohort, suggesting that different pathobiological mechanisms may underscore each subtype.

Gasdermine E-Dependent Mitochondrial Pyroptotic Pathway in Dermatomyositis: A Possible Mechanism of Perifascicular Atrophy

Different mechanisms have been proposed to explain the pathological basis of perifascicular atrophy (PFA), a pathognomonic histologic feature of dermatomyositis (DM); however, the detailed mechanisms remain to be elucidated. There is mitochondrial dysfunction in PFA and expression of mitochondrial apoptosis molecules has been reported in DM. Overexpression of gasdermin E (GSDME) can turn mitochondrial apoptosis to mitochondrial pyroptosis, a newly characterized form of programmed cell death. We determined the expression of proteins involved in the caspase-3- and GSDME-dependent mitochondrial pyroptotic pathway, including BAX, BAK, cytochrome C, caspase-9, caspase-3, GSDME, and IL-1α, in biopsied muscles from DM and control patients. Immunohistochemical analysis showed that those markers were expressed in most fibers in PFA in DM. GSDME-positive and IL-1α-positive staining was mainly localized around punched-out vacuoles or sarcolemma. These markers were significantly upregulated at the protein and mRNA levels in DM versus controls. Our results suggest that caspase-3- and GSDME-dependent mitochondrial pyroptosis are involved in the pathogenetic mechanisms of PFA in DM and that targeting GSDME-dependent mitochondrial pyroptosis may be an effective therapeutic approach for this condition.

Sarcoplasmic MxA expression

Objective:To evaluate the diagnostic value of myxovirus resistance A (MxA) expression in the cytoplasm of myofibers in the diagnosis of dermatomyositis (DM).Methods:We assessed the sensitivity and specificity of the sarcoplasmic expression of MxA in muscles with DM by immunohistochemistry in consecutive cases of DM (n = 34) and other idiopathic inflammatory myopathies (n = 120: 8 with polymyositis, 16 with anti–tRNA-synthetase antibody–associated myositis, 46 with immune-mediated necrotizing myopathy, and 50 with inclusion body myositis) and compared them with conventional pathologic hallmarks of DM, including perifascicular atrophy (PFA) and membrane attack complex (MAC) deposition on endomysial capillaries.Results:The sensitivity and specificity of sarcoplasmic MxA expression were 71% and 98%, respectively. While the specificity was almost comparable to that of PFA and capillary MAC deposition, the sensitivity was higher, with PFA showing 47% sensitivity and 98% specificity and capillary MAC deposition showing 35% sensitivity and 93% specificity. Of note, in patients with DM with typical skin rash but no PFA, 44% of the samples showed sarcoplasmic MxA expression, which was higher than the 17% sensitivity of capillary MAC deposition in the population.Conclusions:Sarcoplasmic MxA expression detected by immunohistochemistry is a more sensitive marker of DM than the conventional hallmarks, indicating its practical utility in the diagnosis of DM. It may well be included in the routine immunohistochemistry panel for myositis.Classification of evidence:This study provides Class II evidence that immunohistochemistry-detected sarcoplasmic MxA expression accurately identifies patients with dermatomyositis.

Polymyositis

ABSTRACT Polymyositis is an uncommon inflammatory disease that causes muscle weakness affecting both sides of the body, typically the proximal muscles. Most commonly, it affects adults in their 30s, 40s, or 50s. Signs and symptoms usually develop gradually, over weeks or months. Raised creatinine phosphokinase (CPK) levels are commonly seen during the acute phase. The electromyogram characteristically shows a myopathic pattern. The affected muscles histopathologically demonstrate endomysial inflammation, lymphocytic infiltration, zonalmyofibrillar loss, and perifascicular atrophy. We report a male patient with a classical presentation of polymyositis. How to cite this article Cheema YS, Gupta P, Attri S, Jamdagni V, Mittal D. Polymyositis. J Postgrad Med Edu Res 2016;50(4):199-200.

The Prevalence of Individual Histopathologic Features Varies according to Autoantibody Status in Muscle Biopsies from Patients with Dermatomyositis

Objective.Individual dermatomyositis (DM)-associated autoantibodies are associated with distinct clinical phenotypes. This study was undertaken to explore the association of these autoantibodies with specific muscle biopsy features.Methods.DM subjects with a muscle biopsy reviewed at Johns Hopkins had sera screened for autoantibodies recognizing Mi-2, transcriptional intermediary factor 1-γ (TIF1-γ), NXP2, MDA5, Ro52, PM-Scl, and Jo1. We also included anti-Jo1–positive patients with polymyositis (PM) who had a biopsy read at Johns Hopkins. Analyzed histological features included perifascicular atrophy, perivascular inflammation, mitochondrial dysfunction, primary inflammation, and myofiber necrosis. Duration of disease, biopsy location, and treatment at biopsy were also analyzed.Results.We studied 91 DM and 7 anti-Jo1–positive patients with PM. In univariate analyses, TIF1-γ+ patients had more mitochondrial dysfunction (47% vs 18%; p = 0.05), NXP2+ patients had less primary inflammation (0% vs 28%; p = 0.01), Mi-2+ patients had more primary inflammation (50% vs 19%; p = 0.03), and PM-Scl+ patients had more primary inflammation (67% vs 18%; p = 0.004) than those who were negative for each autoantibody. Although reliability was limited because of small sample numbers, multivariate analysis confirmed that TIF1-γ+ patients had more mitochondrial dysfunction [prevalence ratio (PR) 2.6, 95% CI 1.0–6.5, p = 0.05] and PM-Scl+ patients had more primary inflammation (PR 5.2, 95% CI 2.0–13.4; p = 0.001) independent of disease duration at biopsy, biopsy site, and treatment at biopsy. No differences in muscle biopsy features were noted between anti-Jo1–positive patients diagnosed with DM and PM.Conclusion.The prevalence of different histological features varies according to autoantibody status in DM. Muscle biopsy features are similar in anti-Jo1 patients with and without a rash.