Diagnosis Of Idiopathic Inflammatory Myopathies Research Articles

Pulmonary impairment, not muscle injury, is associated with elevated ESR in the idiopathic inflammatory myopathies

Pulmonary impairment, not muscle injury, is associated with elevated ESR in the idiopathic inflammatory myopathies

Classification, Diagnosis, and Management of Idiopathic Inflammatory Myopathies

The detection and characterization of a large array of autoantibodies, including at least 8 different antisynthetase, anti-SRP, -200/100 (HMGCR), -Mi-2, -CADM-140 (MDA5), -SAE, -p155, -MJ (NXP-2), and -PMS1, frequently associated with distinct and well-defined clinicopathological features, allowed for significant improvement in the definition and diagnosis of idiopathic inflammatory myopathies (IIM). Classification remains difficult, with lingering divergence between the different specialties involved in IIM care, but several categories clearly stand out, including dermatomyositis (DM), overlap myositis (OM), polymyositis, necrotizing myositis, and sporadic inclusion body myositis (s-IBM). Biopsy and histological analysis remain crucial, particularly in the absence of autoantibodies, to accurately specify the diagnosis and rule out mimics such as muscular dystrophies and metabolic myopathies. Numerous infectious agents (in particular human immunodeficiency virus and human T cell lymphotrophic virus-1) and drugs (statins, tumor necrosis factor inhibitors, and proton pump inhibitors) can cause mimic IIM that must also be excluded. Pharmacological treatment, in addition to glucocorticoids and immunoglobulins, now includes mycophenolate mofetil and rituximab, which proved helpful in resistant cases, particularly rituximab in DM and OM. Exercise, initially seen as potentially deleterious, recently was shown to be efficacious and safe. IIM can thus be reasonably well controlled in most cases, although aggressive disease remains refractory to treatment, including some cases of necrotizing myopathy. Sporadic IBM still seems resistant to all medications tested to date.

A10.3 Arthritis in Patients with Idiopathic Inflammatory Myopathies

<h3>Background and Objectives</h3> Arthritis in idiopathic inflammatory myopathies (IIM) is frequently observed in clinical practise, but, to our knowledge, there is lack of systemic reports of prevalence and/or characteristics of arthritis in myositis patients. The aim of this study is to determine prevalence of arthritis in IIM patients; it’s relation to the course of the muscle disease; characteristics of arthritis with respect to seriousness, distribution and extent as well as it’s relation to autoantibody profiles and others disease’s characteristics. <h3>Materials and Methods</h3> In this cross-sectional study, clinical aspects of disease, history of arthritis and autoantibody profiles were obtained from 106 consecutive patients with definite diagnosis of IIM. In all of them the 68-joint index was investigated. In 55 IIM patients and in 60 control patients with rheumatoid arthritis (RA) German Ultrasound Score 7 (US-7) was performed. <h3>Results</h3> Arthritis at any time of course of myositis occurred in 65 patients (61.3%); 42 had arthritis at the beginning of myositis (in 22 patients before and in 16 together with onset of muscle weakness). 52 patients presented arthritis at clinical examination (25 poly-, 17 oligo-, and 10 with monoarthritis). Most frequently affected joints were wrists (21.7%) and shoulders, metacarpophalangeal, and proximal interphalangeal joints (20.8%). From 29 anti-Jo-1 positive patients 28 had arthritis and significant association between arthritis and anti-Jo-1 positivity was found <i>(p</i> &lt; 0.0001<i>)</i>. 39 out of 55 (70.9%) patients had Gray-Scale (GS) synovitis on ultrasound; in 34 of them also Power-Doppler (PD) positivity was found. Only 4 patients had ultrasonographic tenosynovitis and 3 had bony erosions. From 60 RA patients 57 (95%) had GS synovitis, which was PD-active in 54. Tenosynovitis was found in 25 patients. 25 RA patients had one or more joint erosions. Mean US-7 score as well as scores of individual joints or modality subscores were significantly lower in IIM than in RA, but, when compared only those patients with positive findings, the differences were found in total US-7 score, and GS-synovitis and PD-tenosynovitis subscores, but not in PD-synovitis, GS-tenosynovitis as well as in scores of individual joints. <h3>Conclusions</h3> Our data suggest that arthritis is common feature of myositis. It is often present at the beginning of muscular manifestation of disease, or it even precedes the onset of muscle weakness. Most common presentation is symmetrical, non erosive polyarthritis affecting particularly wrists, shoulders, metacarpophalangeal and proximal interphalangeal joints of the hands. We confirmed strong association of arthritis with anti-Jo-1 antibody. Ultrasound investigation of joint involvement in IIM shows less frequent involvement than in RA, but comparable activity of synovitis measured by PD in affected joints. IIMs have less erosions and tenosynovitis than RA.

Correlation of Clinicoserologic and Pathologic Classifications of Inflammatory Myopathies

The idiopathic inflammatory myopathies (IIM) are acquired muscle diseases characterized by muscle weakness and inflammation on muscle biopsy. Clinicoserologic classifications do not take muscle histology into account to distinguish the subsets of IIM. Our objective was to determine the pathologic features of each serologic subset of IIM and to correlate muscle biopsy results with the clinicoserologic classification defined by Troyanov et al, and with the final diagnoses. We retrospectively studied a cohort of 178 patients with clinicopathologic features suggestive of IIM with the exclusion of inclusion body myositis. At the end of follow-up, 156 of 178 cases were still categorized as IIM: pure dermatomyositis, n = 44; pure polymyositis, n = 14; overlap myositis, n = 68; necrotizing autoimmune myopathy, n = 8; cancer-associated myositis, n = 18; and unclassified IIM, n = 4. The diagnosis of IIM was ruled out in the 22 remaining cases. Pathologic dermatomyositis was the most frequent histologic picture in all serologic subsets of IIM, with the exception of patients with anti-Ku or anti-SRP autoantibodies, suggesting that it supports the histologic diagnosis of pure dermatomyositis, but also myositis of connective tissue diseases and cancer-associated myositis. Unspecified myositis was the second most frequent histologic pattern. It frequently correlated with overlap myositis, especially with anti-Ku or anti-PM-Scl autoantibodies. Pathologic polymyositis was rare and more frequently correlated with myositis mimickers than true polymyositis. The current study shows that clinicoserologic and pathologic data are complementary and must be taken into account when classifying patients with IIM patients. We propose guidelines for diagnosis according to both clinicoserologic and pathologic classifications, to be used in clinical practice.

G.P.65 Epidemiological study of malignancy-associated myositis in Japan

Abstract To analyze the temporal relationships between the development of malignancies and the onset of idiopathic inflammatory myopathy (IIM), and to determine the types of malignancy associated with IIM. The clinical records of 218 consecutive patients with IIM hitopathologically diagnosed in our laboratory were reviewed. The diagnosis of IIM was based on muscle biopsy findings: inflammatory changes with necrotic and/or regenerating fibers, and MHC class 1 antigen expression on non-necrotic fibers. The IIM patients who had a history of malignancies or who developed malignancies during the course of IIM were identified. After identifying these patients with associated malignancies, the temporal relationships between the development of malignancies and the onset of IIM, and the types of associated malignancy, were analyzed. Among the 218 patients (M: 76, F: 142), 68 had skin rash (dermatomyositis) (M: 25, F: 43) and 150 did not have skin rash (polymyositis) (M: 51, F: 99). Among the 218 patients, 62 (28%) [29 (42%) out of 68 patients with rash, and 33 (22%) out of 150 patients without rash, OR 2.6, P = 0.003] were associated with malignancies. The analysis of these 62 patients showed that 41 (77%) developed malignancies within three years of the onset of IIM, and 46 (74%) patients developed IIM before the identification of malignancies. The types of malignancy were gastric (12), breast (8), lung (7), colon (5), bladder (4), hepatocellular (4), uterine cervical (4), and hematological (4) malignancies. Histopathologically, adenocarcinoma was the most frequent subtype. The IIM patients without other associated collagen diseases were found to have a high risk of malignancies (OR 2.18, P = 0.04). IIM patients with typical skin rash and without other associated collagen diseases have a higher risk of developing malignancies. Malignancies that develop within three years of the onset of IIM were more likely to be associated with IIM.

Anti-SAE antibodies in autoimmune myositis: Identification by unlabelled protein immunoprecipitation in an Italian patient cohort

IntroductionMyositis specific autoantibodies (MSAs) are useful in the diagnosis of idiopathic inflammatory myopathies and in the definition of disease subsets. The aim of this study was to set up an unlabelled protein immunoprecipitation technique for MSA identification in the sera of myositis patients, in order to identify and investigate new antibody reactivity, undetectable by currently used methods. MethodsSera of 183 patients with connective tissue diseases (75 adult dermatomyositis, 12 juvenile dermatomyositis, 43 polymyositis, 53 other connective tissue diseases) and 30 healthy controls were screened by an in-house procedure of unlabelled protein immunoprecipitation. In the same sera MSAs and myositis associated antibodies were determined by immunoblotting and immunoprecipitation for RNA. ResultsThe analytical specificity of unlabelled protein immunoprecipitation was demonstrated by testing reference sera with known antibody reactivity.Sera from five patients, affected with dermatomyositis (5/75=7%), immunoprecipitated two proteins of 40 and 90kDa apparent molecular weights respectively, consistent with the subunits of the small ubiquitin like modifier activating enzyme heterodimer (SAE1/SAE2). The identity of putative SAE immunoprecipitated proteins was confirmed by immunoblotting on immunoprecipitates using commercial monospecific antibodies to SAE1 and SAE2. Major clinical features were compared between anti-SAE positive and negative patients. Interestingly, anti-SAE positive patients had mainly skin and muscle manifestations while dysphagia, interstitial lung disease, arthritis and constitutional symptoms were absent. ConclusionsUnlabelled protein immunoprecipitation is a specific analytical approach, appropriate for the identification of the recently described anti-SAE autoantibody. We confirmed the role of anti-SAE antibody as marker of dermatomyositis.

Incidence and prevalence of idiopathic inflammatory myopathies among commercially insured, Medicare supplemental insured, and Medicaid enrolled populations: an administrative claims analysis

BackgroundIdiopathic inflammatory myopathies (IIMs) are a rare group of autoimmune syndromes characterized by chronic muscle inflammation and muscle weakness with no known cause. Little is known about their incidence and prevalence. This study reports the incidence and prevalence of IIMs among commercially insured and Medicare and Medicaid enrolled populations in the US.MethodsWe retrospectively examined medical claims with an IIM diagnosis (ICD-9-CM 710.3 [dermatomyositis (DM)], 710.4 [polymyositis (PM)], 728.81[interstitial myositis]) in the MarketScan® databases to identify age- and gender-adjusted annual IIM incidence and prevalence for 2004–2008. Sensitivity analysis was performed for evidence of a specialist visit (rheumatologist/ neurologist/dermatologist), systemic corticosteroid or immunosuppressant use, or muscle biopsy.ResultsWe identified 2,990 incident patients between 2004 and 2008 (67% female, 17% Medicaid enrollees, 27% aged ≥65 years). Overall adjusted IIM incidence for 2004–2008 for commercial and Medicare supplemental groups combined were 4.27 cases (95% CI, 4.09-4.44) and for Medicaid, 5.23 (95% CI 4.74-5.72) per 100,000 person-years (py). Disease sub-type incidence rates per 100,000-py were 1.52 (95% CI 1.42-1.63) and 1.70 (1.42-1.97) for DM, 2.46 (2.33-2.59) and 3.53 (3.13-3.94) for PM, and 0.73 (0.66-0.81) and 0.78 (0.58-0.97) for interstitial myositis for the commercial/Medicare and Medicaid cohorts respectively. Annual incidence fluctuated over time with the base MarketScan populations. There were 7,155 prevalent patients, with annual prevalence ranging from 20.62 to 25.32 per 100,000 for commercial/Medicare (83% of prevalent cases) and from 15.35 to 32.74 for Medicaid.ConclusionsWe found higher IIM incidence than historically reported. Employer turnover, miscoding and misdiagnosing, care seeking behavior, and fluctuations in database membership over time can influence the results. Further studies are needed to confirm the incidence and prevalence of IIM.

Mortality and its predominant causes in a large cohort of patients with biopsy‐determined inflammatory myositis

There is a paucity of literature on the patterns and predictors of mortality in idiopathic inflammatory myopathies (IIM). To determine the patterns and predictors of mortality in a South Australian cohort of patients with biopsy-proven IIM. The living/deceased status (and for deceased patients the causes of death) of patients with histologically determined IIM was determined from the Births, Deaths and Marriages Registry. Standardised mortality ratios (SMR) were generated compared with the age/gender matched South Australian population. The effect of presence/absence of the components of the Bohan and Peter criteria on risk ratios (RR) for mortality was determined. The effect of comorbidities and autoantibodies on mortality was investigated. The SMR for mortality in IIM was 1.75 and was significantly increased in all disease subgroups, being highest in patients with dermatomyositis (2.40). Dominant causes of death were cardiovascular disease (31%), infections (22%) and malignancy (11%). Risk factors for death were age at time of biopsy (hazard ratio 1.05), ischaemic heart disease (RR 2.97, P < 0.0001), proximal weakness at diagnosis (RR 1.8, P= 0.03), definite diagnosis of IIM per the Bohan and Peter criteria (RR 2.14, P < 0.0001), and the absence of autoantibodies (RR 1.9, P < 0.001). Patients with IIM are at 75% increased risk for mortality, and cardiovascular diseases account for the commonest causes of death. This study suggests a thorough cardiovascular evaluation of these patients is indicated, and raises the possibility that targeted interventions such as the use of aspirin or statins may improve outcomes in IIM.

Anti-NXP2 autoantibodies in adult patients with idiopathic inflammatory myopathies: possible association with malignancy

ObjectivesMyositis-specific autoantibodies (MSAs) are useful tools for identifying clinically homogeneous subsets and predicting prognosis of patients with idiopathic inflammatory myopathies (IIM) including polymyositis (PM) and dermatomyositis (DM). Recent studies have...

PET/CT imaging in inflammatory myopathies

Inflammatory muscle diseases are a group of muscle disorders characterized by muscle weakness, fatigue, and an association with malignancy and paraneoplastic syndrome. A diagnosis of idiopathic inflammatory myopathy is suggested by abnormal myometry and rising creatine kinase, but tissue diagnosis is also needed. Magnetic resonance imaging (MRI) helps localize the appropriate site of biopsy, demonstrate the extent of muscle involvement, and monitor the response to therapy. However, the sensitivity of magnetic resonance (MR) is limited, and whole-body imaging is still far from routine. [(18) F]Fluoro-desoxy-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) is currently the ultimate metabolic imaging technique for the management of cancer. It has also been shown to detect inflammatory conditions and to monitor their response to treatment. The use of FDG PET in screening for underlying malignancies is widely reported and recommended in patients with paraneoplastic syndrome. Unfortunately, only a few reports have been published to show the value of FDG PET in inflammatory muscle diseases, which as we show herein, deserve further pursuit.

Detection of the membrane attack complex as a diagnostic tool in dermatomyositis

Currently there is no reliable diagnostic marker to distinguish between the subgroups of idiopathic inflammatory myopathies (IIMs), i.e. dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Membrane attack complex (MAC) has been shown to be involved in the pathogenesis of dermatomyositis but its role as a diagnostic marker has not been evaluated. To assess the diagnostic utility of MAC deposition in distinguishing dermatomyositis from other neuromuscular disorders. Immunohistochemical detection of MAC deposition on endomysial microvessels was carried out on 127 muscle biopsies comprising of 21 cases of dermatomyositis, 42 other IIMs and 64 non-IIM neuromuscular diseases. MAC deposition showed a high sensitivity (80.9%) and specificity (85%) to differentiate DM from other IIMs. Its specificity was higher (98.4%) in discriminating DM from non-IIM muscular diseases and IIM from non-IIMs. MAC deposition can serve as a reliable marker to distinguish DM from other IIMs (i.e. PM and IBM) as well as from non-IIM diseases. It can also serve as a useful adjunct in diagnosis of IIMs when there is diagnostic dilemma with their morphologic similarities. These results provide further credence to the long-standing view that MAC-mediated capillary destruction is involved in the immunopathogenesis of DM.

P2.49 Sensitivity and specificity of major histocompatibility complex expression on sarcoplasmic membrane for diagnosis of idiopathic inflammatory myopathies

P2.49 Sensitivity and specificity of major histocompatibility complex expression on sarcoplasmic membrane for diagnosis of idiopathic inflammatory myopathies

Diagnostic performance and validation of autoantibody testing in myositis by a commercial line blot assay

Serological testing for myositis-specific or associated autoantibodies [myositis-specific antibody (MSA) and myositis-associated antibody (MAA)] is useful for the diagnosis of idiopathic inflammatory myopathies (IIMs). However, available assays are neither standardized nor validated. The objective is to evaluate the accuracy of a commercial line blot assay for myositis diagnosis. IgG antibodies against Jo-1, PL-7, PL-12, PM/Scl, Ku, Mi-2 and Ro52 antigens were detected by a line blot and in-house RNA immunoprecipitation or immunoblot. We tested sera from 208 IIM patients, 50 healthy subjects and 180 control patients (11 non-autoimmune myopathy, 23 muscular dystrophy, 11 UCTD, 68 SLE, 36 SSc, 22 SS and 9 arthropathy). MSAs or MAAs were detected in 98 (47%) out of the 208 IIM patients by line blot: anti-Jo-1 in 43 (21%), anti-PL-7 or anti-PL-12 in 8 (4%), anti-Mi-2 in 9 (4%), anti-PM/Scl in 9 (4%), anti-Ku in 10 (5%) and anti-Ro52 in 49 (24%). Overall specificity was: 100% for anti-Jo-1, anti-PL-7 or PL-12 and anti-PM/Scl; 96% for anti-Ku; 98% for anti-Mi-2; and 76% for anti-Ro52. In-house testing confirmed line blot results regarding anti-Jo-1, anti-PM/Scl and anti-Ku, while it was more accurate than line blot in detecting anti-Mi-2 (7 vs 4% sensitivity, 100 vs 98% specificity), and anti-aminoacyl-tRNA synthetase (anti-ARS) non-Jo-1 antibodies (11 vs 4% sensitivity, 97 vs 99% specificity). Line blot could be a suitable serological test in the diagnostic workup for myositis, and it represents a reliable alternative to more time-consuming procedures. Continuous effort is recommended in order to improve its accuracy.

Malignancies associated with dermatomyositis and polymyositis in Taiwan: a nationwide population-based study

Previous studies showed that idiopathic inflammatory myopathies (IIM) carried an increased risk of cancers. However, no large-scale study of IIM has been conducted in the Chinese population. We sought to delineate the association of IIM and various cancer types from a nationwide database in Taiwan. We analysed the published national data from records of National Health Insurance claims. Cases of dermatomyositis (DM) and polymyositis (PM) from 2000 to 2005 and cancers registered in the catastrophic illness profile from 1997 to 2006 were collected. A nationally representative cohort of 1,000,000 enrollees was included for comparison. In total, 136 patients (12.8%) among 1059 cases of DM and 46 persons (7.0%) among 661 cases of PM carried internal malignancies. Patients with DM tended to have cancers of nasopharynx, lung and breast. On the other hand, patients with PM tended to have breast, uterine cervix and lung cancers. Compared with the general population, DM gave a 10-fold increased risk for cancers, in which a 66-fold increased risk for nasopharyngeal carcinoma and a 31-fold increased risk for lung cancer were the two most significant. For patients with PM, a 6-fold increased risk for cancer was observed. Juvenile DM had a 16-fold increased risk for haematopoietic or lymphoid malignancy. Two thirds of comorbid malignancies were detected shortly after the diagnoses of IIM, within a mean of 1-2 years. Overall, younger patients with IIM carried the highest risk for malignancies, especially those in their twenties and thirties. This is the first large-scale study to report the associated malignancies and the cancer risk of IIM in Taiwan.

Association of idiopathic inflammatory myopathy and Crohn’s disease

We describe a rare case of concurrent polymyositis and Crohn's disease in a female patient. A 69-year-old female presented in December 2007 with a 5-month history of proximal muscle weakness, pain, fatigue and difficulty in walking and swallowing. Blood tests revealed elevated creatine kinase (3,429 U/l) and lactate dehydrogenase (2,013 U/l) levels. Magnetic resonance imaging found lumbar disc protrusion. Review by immunologists showed a diagnosis of idiopathic inflammatory myopathy. Though electromyography and muscle biopsy at this point were non-specific, corticosteroid treatment was commenced. Her condition worsened precipitously leading to hospitalisation under immunologists. As the provisional diagnosis was polymyositis, we commenced 1.5 mg/kg per day corticosteroid but her muscle power did not improve. Recurrent abdominal symptoms lead to ultrasonography showing intestinal inflammation. While tumour markers were elevated, thorough investigation failed to identify a tumour. Corticosteroid therapy was continued. Persistent abdominal symptoms lead to repeat colonoscopy and biopsy confirming Crohn's disease. Repeat electromyography and muscle biopsy confirmed the diagnosis of polymyositis. Her corticosteroids were tapered off and 5-aminosalicylic acid and azathioprine were started. Her myositic symptoms gradually abated with improvement in her Crohn's disease. She is now able to walk independently and takes 8 mg/day corticosteroids and her muscle enzyme levels are normal. Remember rare systemic associations when dealing with immune-mediated disease. Consider myositis in the differential diagnosis of Crohn's disease associated myopathy. Treating Crohn's disease may lead to improvement in steroid-resistant myositis where the two are associated.

Deep Venous Thrombosis in Dermatomyositis

To the Editor: Recent reports suggest a marked increase in incidence of venous thromboembolism (deep vein thrombosis, DVT) in patients withWegener’s granulomatosis1, a finding that has not been explained by common risk factors for thrombophilia2. To our knowledge, an increased incidence of DVT in patients with idiopathic inflammatory myopathy (IIM) has not previously been reported. We describe our experience with a small cohort of patients with IIM. On review of our hospital electronic medical record (with approval from the institutional review board), 54 patients with a diagnosis of IIM were identified from January 1999 to December 2007. IIM was diagnosed ...

Multiplex Immunoassay Analysis of Cytokines in Idiopathic Inflammatory Myopathy

Abstract Context.—Idiopathic inflammatory myopathies (IIMs), including dermatomyositis, polymyositis, and inclusion-body myositis, can be difficult to diagnose. Objective.—To determine if a multiplex immunoassay for markers of inflammation in muscle homogenates correlates with a diagnosis of IIM. Design.—Frozen archived muscle biopsy specimens from 30 patients with IIM and 34 patients without IIM were homogenized and analyzed for cytokine content with a multiplex microbead-based immunoassay system. Analyte concentrations were normalized to total lysate protein concentration prior to comparison. Results.—Two cytokines, interleukin 1ra and monocyte chemoattractant protein 1, and 1 soluble adhesion molecule, intracellular adhesion molecule 1, were found at significantly greater concentrations in muscle samples from patients with IIM. Intracellular adhesion molecule 1 levels alone were 83% sensitive and 91% specific for IIM at a cutoff of 1240 pg/mg muscle protein. Conclusions.—Immunoassays for selected infla...

Multiplex Immunoassay Analysis of Cytokines in Idiopathic Inflammatory Myopathy

Idiopathic inflammatory myopathies (IIMs), including dermatomyositis, polymyositis, and inclusion-body myositis, can be difficult to diagnose. To determine if a multiplex immunoassay for markers of inflammation in muscle homogenates correlates with a diagnosis of IIM. Frozen archived muscle biopsy specimens from 30 patients with IIM and 34 patients without IIM were homogenized and analyzed for cytokine content with a multiplex microbead-based immunoassay system. Analyte concentrations were normalized to total lysate protein concentration prior to comparison. Two cytokines, interleukin 1ra and monocyte chemoattractant protein 1, and 1 soluble adhesion molecule, intracellular adhesion molecule 1, were found at significantly greater concentrations in muscle samples from patients with IIM. Intracellular adhesion molecule 1 levels alone were 83% sensitive and 91% specific for IIM at a cutoff of 1240 pg/mg muscle protein. Immunoassays for selected inflammatory markers can serve in conjunction with histopathologic analysis as sensitive and specific tools for the diagnosis of IIM.

Major histocompatibility complex class I expression can be used as a diagnostic tool to differentiate idiopathic inflammatory myopathies from dystrophies

Utility of major histocompatibility complex (MHC) Class I antigen immunostaining was studied to differentiate idiopathic inflammatory myopathies from dystrophies. Forty muscle biopsies including seven dermatomyositis (DM), six polymyositis (PM), two sporadic inclusion body myositis (sIBM), 20 dystrophies (one Duchenne, three Becker's, four alpha, one gamma sarcoglycanopathy, nine limb girdle, one myotonic and one fascioscapulohumeral muscular dystrophy) and five controls were stained with antibody for MHC Class I antigen (Novocastra clone W6/32 HL 1:100 dilution). Polymyositis and sIBM showed MHC class I antigen positivity along sarcolemma of single and small groups of muscle fibers. The regenerating fibers in the perifascicular area in DM showed intense cytoplasmic positivity of MHC class I antigen. Muscle fibers in all dystrophies except regenerating fibers and control normal muscle were negative for MHC. Capillaries and lymphocytes were positive controls. There were no false positives in the study. MHC Class I immunostaining can be used as a complementary diagnostic tool for the diagnosis of idiopathic inflammatory myopathies.

Study of idiopathic inflammatory myopathies with special reference to borderland between idiopathic inflammatory myopathies and muscular dystrophies

Idiopathic inflammatory myopathies (IIMs) form important treatable myopathies, hence it is important to recognize and categorize them. In some cases, the differential diagnosis between IIM and muscular dystrophies can be difficult. To study the clinical and laboratory features of patients with IIMs and compare and contrast this group with limb girdle muscular dystrophies (LGMDs). A prospective study for the period of five years [1999-2004] was undertaken at a tertiary neuromuscular center. Bohan and Peter criteria were used for the diagnosis of IIM and Bushby criteria were used for the diagnosis of LGMD. Patients underwent history, clinical examination, hematological tests, electrophysiological studies and muscle biopsy. The biopsies were studied for histology and immunocytochemistry. A clinical scoring system was evolved to differentiate IIM from LGMD and was validated in a blinded manner. Receiver operator curves were used as the statistical method to analyze the sensitivity and specificity. In the IIM group, dermatomyositis was most common, followed by polymyositis, occurring in young females. Overlap group was less common. In patients with polymyositis, onset in upper girdle was associated with adverse outcome. The scoring system helped to differentiate IIM from LGMD, mainly using clinical pointers. This was particularly valuable in chronic cases.