Geographical Latitude Remains as an Important Factor for the Prevalence of Some Myositis Autoantibodies: A Systematic Review

The idiopathic inflammatory myopathies (IIM) are characterized by muscular weakness, cutaneous manifestations, muscle damage revealed by increase of muscular enzymes, muscle biopsy, electromyography and changes on magnetic resonance imaging. However, the hallmark of these IIM, is the development of myositis specific antibodies (MSA) or myositis associated antibodies (MAA). The theories about their presence in the serum of IIM is not known. Some studies have suggested that some of these MSA, such as anti-Mi-2 increases according to the intensity of UV radiation. There is scarce information about the environmental factors that might contribute in order to be considered as triggering factors as UV radiation might be. In this review, we analyzed the reported prevalence of MSAs and MAAs regarding to their geographical location and the possible relation with UV radiation. We collected the prevalence data of fifteen MSA and thirteen MAA from 22 countries around the world and we were able to observe a difference in prevalence between countries and continents. We found differences in anti-PL7, anti-Ro52, anti-La and anti-Ku prevalence according to UV radiation level. Otherwise, we observed that anti-Mi-2 prevalence increases near to the Equator meanwhile anti-MJ/NXP2 and anti-ARS prevalence had an opposite behavior increasing their prevalence in the geographical locations farther to the Equator. Our results highlighted the importance to include the UV radiation and other environmental factors in IIM studies, in order to clarify its association with MSA and MAA prevalence as well as its possible role in the immunopathogenesis of these diseases.

Favorable Response in Statin-Naive Paraneoplastic Anti-HMGCR Antibody-Associated Myopathy to Single Dose of Rituximab and Persistent Remission With Management of Underlying Lung Cancer

Anti-HMGCR myopathy is a subtype of immune-mediated necrotizing myopathy, typically associated with exposure to statins, although a sizable minority in some cohorts are statin-naive. Although the clinical features of acute- or subacute-onset symmetrical proximal muscle weakness mimic those of other idiopathic inflammatory myopathies, necrotizing myopathy is distinguished by the histopathological findings of muscle fiber necrosis and regeneration with little to no accompanying inflammation. Several recent studies of patients with anti-HMGCR myopathy have identified a slightly increased risk of cancer. Most patients require aggressive immunotherapy, usually as a combination of 2 or 3 immunosuppressant drugs. We report a case of a statin-naive paraneoplastic anti-HMGCR myopathy, who unlike other reported cases, responded to a single dose of 1000 mg of intravenous rituximab and subsequent chemoradiation therapy for an underlying lung cancer, despite failing to completely respond to prior high-dose oral prednisone and methotrexate.

Neurological Complications in Patients with Systemic Lupus Erythematosus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is commonly associated with neurological manifestations. Rapid recognition and treatment of these complications may improve outcomes. In this article, we review the neurological conditions associated with SLE, their diagnosis and management strategies.

RECENT FINDINGS

Recent meta-analysis showed that patients with neuropsychiatric manifestations of SLE were more likely to have positive antiphospholipid, antiribosomal P, and antineuronal antibodies. Another meta-analysis showed an association between SLE and antiphospholipid antibodies with cognitive impairment. Two large retrospective studies have shown that the peripheral nervous system is commonly involved in SLE frequently alongside the central nervous system. Neurological manifestations occur in most of SLE patients. Antiphospholipid antibodies are common in patients with SLE and increase the odds of neurological complications. Management typically involved a combination of treatments directed toward the neurological complication and therapies directed toward SLE itself. The efficacy of these treatment protocols, however, has not been rigorously studied and deserves further investigation.

Clinical spectrums and outcomes of necrotizing autoimmune myopathy versus other idiopathic inflammatory myopathies: a multicenter case-control study

OBJECTIVE

To investigate the clinical characteristics, laboratory features, and treatment outcomes of Thai patients compared between those with necrotizing autoimmune myopathy (NAM) and those with other idiopathic inflammatory myopathies (IIMs) or non-NAM.

METHODS

This multicenter case-control study included patients aged ≥ 18 years who were diagnosed with IIMs by muscle pathology, and who had relevant clinical and laboratory data, including muscle enzymes, from at least 3 follow-up visits during a 1-year period. Baseline clinical and laboratory data were recorded. Serum myositis-specific autoantibodies (MSAs) were obtained on the date of recruitment.

RESULTS

Of the 70 included patients, 67% had NAM, and 33% had non-NAM. The mean age of patients was 50.5 ± 15.9 years, 67% were female, and the median duration of symptoms was 2 months (IQR, 1-4). History of cancer was significantly higher in non-NAM (21.7% vs. 2.1%, p = 0.01). Gottron's papules were significantly more prevalent in non-NAM (21.7% vs. 4.3%, p = 0.04). Non-NAM had a higher prevalence of anti-Mi-2a (17.4% vs. 2.1%, p = 0.04) and Mi-2b (17.4% vs. 0.0%, p = 0.01); however, the presence of other MSAs, including anti-HMGCR and anti-SRP, was similar between groups. Improvement in motor power and treatment intensification with glucocorticoid and/or immunosuppressive agents 3 times throughout the follow-up period was similar between groups (NAM 46.8% vs. non-NAM 34.8%, p = 0.34).

CONCLUSION

NAM is indistinguishable from non-NAM by clinical manifestations, serology, or laboratory findings, except that pathognomonic skin sign of Gottron's papules and anti-Mi2 are suggestive of dermatomyositis. The integration of clinical, serological, and pathological data is essential for making a diagnosis of NAM.Key Points• NAM is indistinguishable from non-NAM by clinical manifestations, serology, or laboratory findings.• The integration of clinical, serological, and pathological data is essential for making a diagnosis of NAM.

Immune-mediated necrotising myopathy: A critical review of current concepts

Immune-mediated necrotising myopathy (IMNM) is a relatively recently described form of idiopathic inflammatory myopathy (IIM) that is characterised by progressive proximal weakness and few extra-muscular manifestations. Prominent myonecrosis, muscle fibre regeneration and a relative paucity of intramuscular lymphocytes are seen histologically. Immunological mechanisms are believed to underpin the pathogenesis, and intense immunotherapy is frequently required. Disease is often severe and neuromuscular recovery may be poor. Recently there has been an impressive international research effort to understand and characterise this emerging condition, although much remains unknown. Significant advances in the field include the discovery of specific autoantibodies, increased understanding of the risk factors, clinical characteristics and treatment options owing to a wealth of observational studies, and the development of novel classification criteria. Herein we review the current evidence regarding the pathophysiology, clinical presentation, histological features and serological profiles associated with this condition. Diagnostic approaches are discussed, including the role of muscle MRI and antibodies targeting 3‑hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and signal-recognition peptide (SRP), and a review of current treatment recommendations is provided.

Bench to bedside review of myositis autoantibodies

Idiopathic inflammatory myopathies represent a heterogeneous group of autoimmune diseases with systemic involvement. Even though numerous specific autoantibodies have been recognized, they have not been included, with the only exception of anti-Jo-1, into the 2017 Classification Criteria, thus perpetuating a clinical-serologic gap. The lack of homogeneous grouping based on the antibody profile deeply impacts the diagnostic approach, therapeutic choices and prognostic stratification of these patients. This review is intended to highlight the comprehensive scenario regarding myositis-related autoantibodies, from the molecular characterization and biological significance to target antigens, from the detection tools, with a special focus on immunofluorescence patterns on HEp-2 cells, to their relative prevalence and ethnic diversity, from the clinical presentation to prognosis. If, on the one hand, a notable body of literature is present, on the other data are fragmented, retrospectively based and collected from small case series, so that they do not sufficiently support the decision-making process (i.e. therapeutic approach) into the clinics.

Necrotizing Autoimmune Myopathy: A Unique Subset of Idiopathic Inflammatory Myopathy

Necrotizing autoimmune myopathy (NAM) is a recently recognized entity within the spectrum of idiopathic inflammatory myopathies. Diagnosis critically rests on histopathologic demonstration of macrophage predominant myocyte destruction, with few to no lymphocytes. We report our experience with identifying and treating this subset of inflammatory myositis, highlighting the importance of muscle biopsy in diagnosis, association with statin use and malignancy, and challenges of therapy.We present 3 cases that presented to 2 hospitals within our academic system in calendar year 2014 with acute/subacute onset of profound proximal muscle weakness and markedly elevated creatine kinase levels. All patients had been exposed to statins for varying periods. While each electromyogram (EMG) study showed changes with a diffuse inflammatory myopathy, it was not until muscle biopsy was performed when histopathologic features consistent with NAM solidified the diagnosis in all 3 cases. While high-dose glucocorticoids helped provide some degree of improvement in symptoms, none of our cases returned to their preillness baseline independent functioning. Additional immunosuppressive therapy was considered in each case but limited because of comorbidities.These cases demonstrate the importance of pursuing muscle biopsy in all patients with proximal muscle weakness and markedly elevated creatine kinase levels. While symptoms appear consistent with polymyositis, only through muscle biopsy can the diagnosis of NAM be made. Statins have been implicated in NAM, acting through an antibody-dependent mechanism. Combination immunosuppressive therapy has been advocated, but our patient's comorbidities precluded safe use of medications beyond glucocorticoids.

A Comprehensive Overview on Myositis-Specific Antibodies: New and Old Biomarkers in Idiopathic Inflammatory Myopathy

Autoantibodies specific for idiopathic inflammatory myopathy (myositis-specific autoantibodies (MSAs)) are clinically useful biomarkers to help the diagnosis of polymyositis/dermatomyositis (PM/DM). Many of these are also associated with a unique clinical subset of PM/DM, making them useful in predicting and monitoring certain clinical manifestations. Classic MSAs known for over 30 years include antibodies to Jo-1 (histidyl transfer RNA (tRNA) synthetase) and other aminoacyl tRNA synthetases (ARS), anti-Mi-2, and anti-signal recognition particle (SRP). Anti-Jo-1 is the first autoantibodies to ARS detected in 15-25 % of patients. In addition to anti-Jo-1, antibodies to seven other aminoacyl tRNA synthetases (ARS) have been reported with prevalence, usually 1-5 % or lower. Patients with any anti-ARS antibodies are associated with anti-synthetase syndrome characterized by myositis, interstitial lung disease (ILD), arthritis, Raynaud's phenomenon, and others. Several recent studies suggested heterogeneity in clinical features among different anti-ARS antibody-positive patients and anti-ARS may also be found in idiopathic ILD without myositis. Anti-Mi-2 is a classic marker for DM and associated with good response to steroid treatment and good prognosis. Anti-SRP is specific for PM and associated with treatment-resistant myopathy histologically characterized as necrotizing myopathy. In addition to classic MSAs, several new autoantibodies with strong clinical significance have been described in DM. Antibodies to transcription intermediary factor 1γ/α (TIF1γ/α, p155/140) are frequently found in DM associated with malignancy while anti-melanoma differentiation-associated gene 5 (MDA5; CADM140) are associated with clinically amyopathic DM (CADM) complicated by rapidly progressive ILD. Also, anti-MJ/nuclear matrix protein 2 (NXP-2) and anti-small ubiquitin-like modifier-1 (SUMO-1) activating enzyme (SAE) are recognized as new DM-specific autoantibodies. Addition of these new antibodies to clinical practice in the future will help in making earlier and more accurate diagnoses and better management for patients.

[Anti-HMG-CoA reductase necrotizing myopathy: A report of 4 cases]

INTRODUCTION

Anti-3-hydroxy-3-méthylglutaryl-coenzyme A reductase antibody-associated necrotizing autoimmune myopathy has been recently described (2011). This myopathy is distinct from statin toxic myopathy. Our objective is to report on the clinical and para-clinical characteristics of this myopathy and to show the difficulties of therapeutic care.

CASE REPORTS

We describe 4 cases of patients followed-up in Brittany, France. All data have been analyzed retrospectively. The mean age of our patients was 59.5 years, with a sex ratio of 1. The clinical presentation was homogeneous, with a subacute painful proximal and symmetrical weakness, without extra-muscular involvement. Other presentations have been described (including pseudo-dystrophic presentation). All patients had a previous statin medication (mean duration of 3.75 years) although this criteria is not a requisite. All patients had high levels of creatine kinase and abnormal electromyographic examination. The pathological pattern on muscular biopsy was a necrotizing myopathy without significant inflammatory cells infiltration. Cardio-respiratory function was normal and no associated neoplasia was found. Over the follow-up, we observed a marked corticosteroid-dependence, not improved by immunosuppressive drugs (azathioprine and methotrexate). The benefit of intravenous immunoglobulin was clear with, sometimes, prolonged responses.

CONCLUSION

An early diagnosis of this myopathy is necessary in order to introduce an immunotherapy associated with a close monitoring. The therapeutic strategy (within which the stead of intravenous immunoglobulin seems increased) remains to be defined and long-term prospective studies are thus needed.

Idiopathic Inflammatory Myopathies: Clinical Approach and Management

Idiopathic inflammatory myopathies (IIM) are a group of chronic, autoimmune conditions affecting primarily the proximal muscles. The most common types are dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myopathy (NAM), and sporadic inclusion body myositis (sIBM). Patients typically present with sub-acute to chronic onset of proximal weakness manifested by difficulty with rising from a chair, climbing stairs, lifting objects, and combing hair. They are uniquely identified by their clinical presentation consisting of muscular and extramuscular manifestations. Laboratory investigations, including increased serum creatine kinase (CK) and myositis specific antibodies (MSA) may help in differentiating clinical phenotype and to confirm the diagnosis. However, muscle biopsy remains the gold standard for diagnosis. These disorders are potentially treatable with proper diagnosis and initiation of therapy. Goals of treatment are to eliminate inflammation, restore muscle performance, reduce morbidity, and improve quality of life. This review aims to provide a basic diagnostic approach to patients with suspected IIM, summarize current therapeutic strategies, and provide an insight into future prospective therapies.

Diagnostic performance of a commercial immunoblot assay for myositis antibody testing

The objective of this study was to establish a population based reference range for a commercial immunoblot assay detecting myositis specific autoantibodies (MSAs) and myositis associated autoantibodies (MAAs), and to assess the diagnostic performance of this reference range against the manufacturer's recommended ranges in a myositis patient cohort. A total of 124 patients from a myositis cohort and 197 healthy controls were serologically assessed using a commercial immunoblot containing eleven autoantigens (Jo-1, EJ, OJ, PL7, PL12, Mi-2, SRP, Ku, PMScl75, PMScl100 and Ro52) according to the manufacturer's instructions. Use of the manufacturer's reference ranges resulted in detection of MSAs in 19.4% of myositis patients and 9.1% of controls; MAAs were detected in 41.1% of myositis patients and 14.2% of controls. Reference values derived from the healthy control population resulted in significant differences in cut-off values for some autoantibodies, particularly Ro52 and PMScl75. Use of local reference ranges reduced detection of MSAs to 16.9% of myositis patients and 3% of healthy controls, with MAAs 23.4% of patients and 2% of healthy controls. Application of population based reference ranges resulted in significant differences in detection of MSAs and MAAs compared to the manufacturer's recommended ranges. Cut-off levels should be assessed to ensure suitability for the population tested.

Signal recognition particle immunoglobulin g detected incidentally associates with autoimmune myopathy

Introduction: Paraneoplastic autoantibody screening of 150,000 patient sera by tissue‐based immunofluorescence incidentally revealed 170 with unsuspected signal recognition particle (SRP) immunoglobulin G (IgG), which is a recognized biomarker of autoimmune myopathy. Of the 77 patients with available information, 54 had myopathy. We describe the clinical/laboratory associations. Methods: Distinctive cytoplasm‐binding IgG (mouse tissue substrate) prompted western blot, enzyme‐linked immunoassay, and immunoprecipitation analyses. Available histories were reviewed. Results: The immunostaining pattern resembled rough endoplasmic reticulum, and mimicked Purkinje‐cell cytoplasmic antibody type 1 IgG/anti‐Yo. Immunoblotting revealed ribonucleoprotein reactivity. Recombinant antigens confirmed the following: SRP54 IgG specificity alone (17); SRP72 IgG specificity alone (3); both (32); or neither (2). Coexisting neural autoantibodies were identified in 28% (low titer). Electromyography revealed myopathy with fibrillation potentials; 78% of biopsies had active necrotizing myopathy with minimal inflammation, and 17% had inflammatory myopathy. Immunotherapy responsiveness was typically slow and incomplete, and relapses were frequent on withdrawal. Histologically confirmed cancers (17%) were primarily breast and hematologic, with some others. Conclusions: Autoimmune necrotizing SRP myopathy, both idiopathic and paraneoplastic, is underdiagnosed in neurological practice. Serological screening aids early diagnosis. Cancer surveillance and appropriate immunosuppressant therapy may improve outcome. Muscle Nerve53: 925–932, 2016

Necrotizing myopathies: an update

Necrotizing myopathy is defined by the predominant pathological feature of necrosis of muscle fibers in the absence of substantial lymphocytic inflammatory infiltrates. Most commonly necrotizing myopathies are divided into immune mediated (IMNM) and nonimmune mediated (NIMNM). IMNM has been associated with anti-signal recognition particle antibodies, connective tissue diseases, cancer, post-statin exposure with 3-hydroxy-3-methylglutaryl-coenzyme A antibodies, and viral infections including HIV and hepatitis C. NIMNM is linked to medications and toxic exposures. Both IMNM and NIMNM are typically characterized by proximal weakness, although the severity can vary substantially. Myalgias are reported by some, but not all, patients. Pathological findings on muscle biopsy include predominant fiber necrosis with little or no inflammatory infiltrate. In IMNM, there is variable evidence for the deposition of membrane attack complex on capillaries and muscle fibers, although membrane attack complex deposition on capillaries is typically less than is seen in dermatomyositis; class I major histocompatibility complex expression on muscle fibers is variable but typically less than is seen in polymyositis. Immunohistochemical abnormalities are not typically seen in NIMNM. Treatment of IMNM involves immunosuppressive therapy, although there are no controlled trials to guide particular treatment choices. Treatment of NIMNM involves removal of the toxic exposure.

[A case of chronic myopathy associated with an antibody to signal recognition particle (SRP) following long-term asymptomatic hypercreatinekinasemia]

A 65-year-old man first visited our hospital due to hypercreatinekinasemia (hyperCKemia) (669 IU/l) 12 years ago at age 53. At that time, he had normal muscle strength without other neurological deficits, electromyography (EMG) was normal, and a muscle biopsy obtained from the biceps brachii was intact in routine histochemical studies. These findings led to a diagnosis of idiopathic hyperCKemia that lasted for over a decade. At age 65, the patient became aware of muscle weakness and serum CK was elevated to 4,846 IU/l. Neurological examination revealed very mild atrophy in both thighs, proximal muscle weakness in the left upper and right lower limbs without myalgia, grasping pain, joint pain, and skin lesions. A typical myogenic pattern was detected on EMG exclusively in proximal limb muscles, and fat-suppressed MRI showed high intensity signal areas in adductor magnus muscles. The clinical diagnosis was limb-girdle muscular dystrophy, but MRI findings suggestive of an inflammatory process prompted us to perform muscle biopsy at the rectus femoris. The pathology had characteristic features of necrotizing myopathy containing necrotic and regenerating fibers without prominent inflammatory cell infiltration. Serum anti-signal recognition particle (SRP) antibodies were found to be positive and the final diagnosis was anti-SRP antibody myopathy. Muscle weakness progressed slowly despite therapy with oral corticosteroids. Addition of intravenous high-dose immunoglobulin therapy led to an apparent improvement of muscle weakness in parallel with lowering of the serum CK level. In those who were thought to be idiopathic hyperCKemia or hereditary muscle disorders, potential immunotherapy-effective group does exist. We suggest considering such cases including anti-SRP antibody myopathy during diagnosis, and non-invasive MRI study may be useful to differentiate immunotherapy-effective group from hereditary muscle disorders.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIM) consist of rare heterogeneous autoimmune disorders that present with marked proximal and symmetric muscle weakness, except for distal and asymmetric weakness in inclusion body myositis. Despite many similarities, the IIM are fairly heterogeneous from the histopathologic and pathogenetic standpoints, and also show some clinical and treatment-response differences. The field has witnessed significant advances in our understanding of the pathophysiology and treatment of these rare disorders. This review focuses on dermatomyositis, polymyositis, and necrotizing myopathy, and examines current and promising therapies.

Clinical and genetic associations of autoantibodies to 3-hydroxy-3-methyl-glutaryl-coenzyme a reductase in patients with immune-mediated myositis and necrotizing myopathy

INTRODUCTION

Inhibition of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) with statins may trigger idiopathic inflammatory myositis (IIM) or immune-mediated necrotizing myopathy (IMNM). Anti-HMGCR antibodies have been detected in patients with IIM/IMNM. We aimed to determine the associations of anti-HMGCR in IIM/IMNM.

METHODS

Anti-HMGCR antibodies were detected by ELISA in sera from patients with IIM/IMNM.

RESULTS

Anti-HMGCR antibodies were detected in 19 of 207 patients with IIM/IMNM, and there was a trend toward an association with male gender (P = 0.079). Anti-HMGCR antibodies were associated strongly with statin exposure (OR = 39, P = 0.0001) and HLA-DRB1*11 (OR = 50, P < 0.0001). The highest risk for development of anti-HMGCR antibodies was among HLA-DR11 carriers exposed to statins. Univariate analysis showed a strong association of anti-HMGCR antibodies with diabetes mellitus (P = 0.008), which was not confirmed by multiple regression. Among anti-HMGCR(+) patients there was a trend toward increased malignancy (P = 0.15).

CONCLUSIONS

Anti-HMGCR antibodies are seen in all subtypes of IIM and IMNM and are associated strongly with statin use and HLA-DR11. Muscle Nerve 52: 196-203, 2015.

Myositis registries and biorepositories: powerful tools to advance clinical, epidemiologic and pathogenic research

PURPOSE OF REVIEW

Clinical registries and biorepositories have proven extremely useful in many studies of diseases, especially rare diseases. Given their rarity and diversity, the idiopathic inflammatory myopathies, or myositis syndromes, have benefited from individual researchers' collections of cohorts of patients. Major efforts are being made to establish large registries and biorepositories that will allow many additional studies to be performed that were not possible before. Here, we describe the registries developed by investigators and patient support groups that are currently available for collaborative research purposes.

RECENT FINDINGS

We have identified 46 myositis research registries, including many with biorepositories, which have been developed for a wide variety of purposes and have resulted in great advances in understanding the range of phenotypes, clinical presentations, risk factors, pathogenic mechanisms, outcome assessment, therapeutic responses, and prognoses. These are now available for collaborative use to undertake additional studies. Two myositis patient registries have been developed for research, and myositis patient support groups maintain demographic registries with large numbers of patients available to be contacted for potential research participation.

SUMMARY

Investigator-initiated myositis research registries and biorepositories have proven extremely useful in understanding many aspects of these rare and diverse autoimmune diseases. These registries and biorepositories, in addition to those developed by myositis patient support groups, deserve continued support to maintain the momentum in this field as they offer major opportunities to improve understanding of the pathogenesis and treatment of these diseases in cost-effective ways.

Diagnosis, pathogenesis and treatment of myositis: recent advances

Dermatomyositis (DM), polymyositis (PM), necrotizing myopathy (NM) and inclusion body myositis (IBM) are four distinct subtypes of idiopathic inflammatory myopathies - in short myositis. Recent studies have shed some light on the unique pathogenesis of each entity. Some of the clinical features are distinct, but muscle biopsy is indispensable for making a reliable diagnosis. The use of magnetic resonance imaging of skeletal muscles and detection of myositis-specific autoantibodies have become useful additions to our diagnostic repertoire. Only few controlled trials are available to substantiate current treatment approaches for myositis and hopes are high that novel modalities will become available within the next few years. In this review we provide an up-to-date overview of the pathogenesis and diagnostic approach of myositis. We aim to present a guide towards therapeutic and general management.

[Autoantibody profile in myositis]

Patients suffering from muscular symptoms or with an increase of creatine kinase levels may present a myopathy. In such situations, clinicians have to confirm the existence of a myopathy and determine if it is an acquired or a genetic muscular disease. In the presence of an acquired myopathy after having ruled out an infectious, a toxic agent or an endocrine cause, physicians must identify which type of idiopathic myopathy the patient is presenting: either a myositis including polymyositis, dermatomyositis, and inclusion body myositis, or an immune-mediated necrotizing myopathy. Histopathology examination of a muscle biopsy is determinant but detection of autoantibody is now also crucial. The myositis-specific antibodies and myositis-associated antibodies lead to a serologic approach complementary to the histological classification, because strong associations of myositis-specific antibodies with clinical features and survival have been documented. The presence of anti-synthetase antibodies is associated with an original histopathologic pattern between polymyositis and dermatomyositis, and defines a syndrome where interstitial lung disease drives the prognosis. Anti-MDA-5 antibody are specifically associated with dermatomyositis, and define a skin-lung syndrome with a frequent severe disease course. Anti-TIF1-γ is also associated with dermatomyositis but its presence is frequently predictive of a cancer association whereas anti-MI2 is associated with the classical dermatomyositis. Two specific antibodies, anti-SRP and anti-HMGCR, are observed in patients with immune-mediated necrotizing myopathies and may be very useful to distinguish acquired myopathies from dystrophic muscular diseases in case of a slow onset and to allow the initiation of effective therapy.

[Necrotizing myopathies: From genetic to acquired forms]

Necrotizing myopathies (NM) are defined by histological features. Muscle biopsy demonstrates marked muscle necrosis with regeneration, with little or an absence of inflammatory infiltrate. Histological pattern of NM is unspecific and can be encountered in diverse conditions as acquired myopathies and muscular dystrophies. Among acquired forms of NM, necrotizing autoimmune myopathy (NAM) is a recently recognized sub-group of the idiopathic inflammatory myopathies. Classically, patients present with a subacute severe proximal myopathy, associated with a markedly elevated creatine kinase level, usually greater than 10 times the upper limit of normal. Nevertheless, the clinical presentation can be misleading, with chronic course mimicking muscular dystrophy. Different forms of NAM can be distinguished with various underlying inciting conditions, including autoantibodies to the SRP, autoantibodies to the HMG-CoA reductase, association to connective tissue disease or underlying malignancy. Other associated conditions need yet to be identified. To confirm a diagnosis of NAM, other causes of NM should be excluded as toxic myopathies, muscular dystrophies and other inflammatory myopathies with a misleading histological pattern. NAM is a rare condition but is probably underdiagnosed. Both clinicoserologic and pathologic data must be taken into account to improve this diagnosis. We propose guidelines for diagnosis of NAM according to clinical course, to be used in clinical practice.

Frequency and spectrum of myopathies in patients with psoriasis

INTRODUCTION

Psoriasis is a T-cell-mediated skin disorder with uncommon extracutaneous manifestations. Rare patients with psoriasis and myopathy have been reported.

METHODS

We conducted a retrospective review of medical records of psoriasis patients seen at the Mayo Clinic during the period from January 1, 1996 to May 31, 2011. Patients who had pathologically confirmed myopathy or lymphocytic infiltrates in muscle were included.

RESULTS

Among 11,370 psoriasis patients, 13 had pathologically confirmed myopathies. Seventy percent were inflammatory myopathies, and 2 had focal inflammation in the muscle. Psoriasis preceded myopathy onset in two-thirds of the patients (median 14.7 years). Half of the patients had psoriatic arthritis; 60% had other autoimmune disorders. Patients who received anti-tumor necrosis factor-alpha (anti-TNF-α) therapy had a higher risk for developing myopathy or inflammation in muscle (odds ratio = 4.45).

CONCLUSIONS

Myopathy or inflammation in muscle affects an average of 1.32 of every 1000 psoriasis patients. Concomitant autoimmune disorders, psoriatic arthritis, and exposure to anti-TNF-α therapy may be associated with increased risk of developing myopathy in psoriasis patients.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies are a group of rare disorders including polymyositis (PM), dermatomyositis (DM), and autoimmune necrotizing myopathies (NMs). The idiopathic inflammatory myopathies share many similarities. They present acutely, subacutely, or chronically with marked proximal and symmetric muscle weakness, except for associated distal and asymmetric weakness in inclusion body myositis. The idiopathic inflammatory myopathies also share a variable degree of creatine kinase (CK) elevation and a nonspecifically abnormal electromyogram demonstrating an irritative myopathy. The muscle pathology demonstrates inflammatory exudates of variable distribution within the muscle fascicle. Despite these similarities, the idiopathic inflammatory myopathies are a heterogeneous group. The overlap syndrome (OS) refers to the association of PM, DM, or NM with connective tissue disease, such as scleroderma or systemic lupus erythematosus. In addition to elevated antinuclear antibodies (ANA), patients with OS may be weaker in the proximal arms than the legs mimicking the pattern seen in some muscular dystrophies. In this review, we focus on DM, PM, and NM and examine current and promising therapies.