Clinical, Biochemical and Histological Responses to Treatment in Polymyositis: A Prospective Study

Evaluating disease status in idiopathic inflammatory myopathies with quantitative muscle ultrasound

INTRODUCTION/AIMS

Muscle strength, functional status, and muscle enzymes are conventionally used to evaluate disease status in idiopathic inflammatory myopathies (IIM). This study aims to investigate the role of quantitative muscle ultrasound in evaluating disease status in IIM patients.

METHODS

Patients with IIM, excluding inclusion body myositis, were recruited along with age- and sex-matched healthy controls (HC). All participants underwent muscle ultrasound and clinical assessments. Six limb muscles were unilaterally scanned using a standardized protocol, measuring muscle thickness (MT) and echo intensity (EI). Results were compared with HC, and correlations were made with outcome measures.

RESULTS

Twenty IIM patients and 24 HC were recruited. The subtypes of IIM were dermatomyositis (6), necrotizing myositis (6), polymyositis (3), antisynthetase syndrome (3), and nonspecific myositis (2). Mean disease duration was 8.7 ± 6.9 years. There were no significant differences in demographics and anthropometrics between patients and controls. MT of rectus femoris in IIM patients was significantly lower than HC. Muscle EI of biceps brachii and vastus medialis in IIM patients were higher than HC. There were moderate correlations between MT of rectus femoris and modified Rankin Scale, Physician Global Activity Assessment, and Health Assessment Questionnaire, as well as between EI of biceps brachii and Manual Muscle Testing-8.

DISCUSSION

Muscle ultrasound can detect proximal muscle atrophy and hyperechogenicity in patients with IIM. The findings correlate with clinical outcome measures, making it a potential tool for evaluating disease activity of patients with IIM in the late phase of the disease.

Decreased Muscular Perfusion in Dermatomyositis: Initial Results Detected by Inflow-Based Vascular-Space-Occupancy MRI

OBJECTIVE. This study aimed to determine whether inflow-based vascular-space-occupancy (iVASO) MRI could reproducibly quantify skeletal muscle perfusion and differentiate patients with dermatomyositis (DM) from healthy subjects. MATERIALS AND METHODS. A total of 25 patients with DM and 22 healthy volunteers underwent iVASO MRI in a 3-T MRI scanner. Maximum and mean arteriolar muscle blood volume (MBV) values of four subgroups of muscles (normal muscles, morphologically normal-appearing muscles, edematous muscles, and atrophic or fat-infiltrated muscles) were obtained. Maximum and mean arteriolar MBV values were compared among the different subgroups, and repeat testing was performed in 20 subjects to assess reproducibility. RESULTS. Compared with normal muscles in healthy subjects, morphologically normal-appearing muscles, edematous muscles, and atrophic or fat-infiltrated muscles in patients with DM showed a significant decrease of both maximum and mean arteriolar MBV (p < .001). Both parameters were significantly lower in atrophic or fat-infiltrated muscles than in morphologically normal-appearing and edematous muscles (p < .001). ROC AUCs for discriminating patients with DM from healthy volunteers were 0.842 and 0.812 for maximum and mean arteriolar MBV values, respectively. As a measure of test-retest studies, the intraclass correlation coefficients (ICCs) were 0.990 (95% CI, 0.986-0.993) and 0.990 (95% CI, 0.987-0.993) for maximum and mean arteriolar MBV, respectively. For interobserver reproducibility, the ICCs were 0.989 (95% CI, 0.986-0.991) and 0.980 (95% CI, 0.975-0.983), respectively. CONCLUSION. iVASO MRI can reproducibly quantify arteriolar MBV in the thigh and discriminate between healthy volunteers and patients with DM.

Ultrasound in the inflammatory myopathies

Dermato- or polymyositis must be diagnosed or ruled out early because early immunosuppressive therapy prevents irreversible muscle degeneration. Acute poly- and dermatomyositis are accompanied by normal or increased size, low echogenicity, and elevated perfusion of affected muscles, whereas in chronic poly- and dermatomyositis, the size and perfusion of affected muscles are reduced and echogenicity is increased. Although magnetic resonance imaging is more sensitive in detecting edema-like muscular changes and thereby acute myositis, contrast-enhanced ultrasound with its capability of measuring perfusion has become a useful diagnostic tool in diagnosing acute inflammation in poly- and dermatomyositis.

Quantitative evaluation of muscle perfusion with CEUS and with MR

Functional imaging might increase the role of imaging in muscular diseases, since alterations of muscle morphology alone are not specific for a particular disease. Perfusion, i.e., the blood flow per tissue and time unit including capillary flow, is an important functional parameter. Pathological changes of skeletal muscle perfusion can be found in various clinical conditions, such as degenerative or inflammatory myopathies or peripheral arterial occlusive disease. This article reviews the theoretical basics of functional radiological techniques for assessing skeletal muscle perfusion and focuses on contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) techniques. Also, the applications of microvascular imaging, such as in detection of myositis and for discriminating myositis from other myopathies or evaluating peripheral arterial occlusive disease, are presented, and possible clinical indications are discussed. In conclusion, dedicated MR and CEUS methods are now available that visualize and quantify (patho-)physiologic information about microcirculation within skeletal muscles in vivo and hence establish a useful diagnostic tool for muscular diseases.

Pathologic Skeletal Muscle Perfusion in Patients with Myositis: Detection with Quantitative Contrast-enhanced US—Initial Results

PURPOSE

To prospectively determine whether contrast material-enhanced ultrasonography (US) can depict inflammation-induced changes in muscle perfusion for patients suspected of having dermatomyositis or polymyositis and to compare these findings with those of magnetic resonance (MR) imaging and muscle biopsy.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Perfusion in skeletal muscles was quantified with contrast-enhanced intermittent power Doppler US by applying a modified model that analyzed the replenishment kinetics of microbubbles. In 22 patients (16 women, six men; mean age, 52 years +/- 17) who were suspected of having myositis and in 10 healthy volunteers (two women, eight men; mean age, 28 years +/- 4), contrast-enhanced US of the clinically affected right biceps muscle was performed to measure blood flow, blood volume, and blood flow velocity. Additionally, the right upper arm was examined with a 1.5-T unit by using three different MR imaging techniques. Findings were compared with the results of clinical examinations and muscle biopsy. Data for perfusion-related parameters obtained at contrast-enhanced US were analyzed by using a nonparametric Mann-Whitney U test.

RESULTS

Eight patients had histologically confirmed myositis and showed significantly higher blood flow velocity (P = .01), blood flow (P = .001), and blood volume (P = .002) at contrast-enhanced US than did patients who did not have myositis. Blood flow velocity (P = .001) and blood flow (P = .002) were significantly higher in patients with myositis than in volunteers. An increase in signal intensity on T2-weighted MR images was found in all patients with myositis, while contrast material enhancement on fat-suppressed T1-weighted MR images was found in only four of seven patients with myositis.

CONCLUSION

Initial results show that contrast-enhanced US is a feasible method for noninvasively demonstrating increased perfusion in the involved muscle groups in patients with myositis.

Autoantibodies to a 140-kd polypeptide, CADM-140, in Japanese patients with clinically amyopathic dermatomyositis

OBJECTIVE

To identify novel autoantibodies specific for dermatomyositis (DM), especially those specific for clinically amyopathic DM (C-ADM).

METHODS

Autoantibodies were analyzed by immunoprecipitation in 298 serum samples from patients with various connective tissue diseases (CTDs) or idiopathic pulmonary fibrosis (IPF). Antigen specificity of the sera was further examined by immunoblotting and indirect immunofluorescence (IF). The disease specificity and clinical features associated with the antibody of interest were determined.

RESULTS

Eight sera recognized a polypeptide of approximately 140 kd (CADM-140 autoantigen) by immunoprecipitation and immunoblotting. Immunoreactivity was detected in the cytoplasm, and indirect IF revealed a granular or reticular pattern. Anti-CADM-140 antibodies were detected in 8 of 42 patients with DM, but not in patients with other CTDs or IPF. Interestingly, all 8 patients with anti-CADM-140 antibodies had C-ADM. Among 42 patients with DM, those with anti-CADM-140 autoantibodies had significantly more rapidly progressive interstitial lung disease (ILD) when compared with patients without anti-CADM-140 autoantibodies (50% versus 6%; P = 0.008).

CONCLUSION

These results indicate that the presence of anti-CADM-140 autoantibodies may be a novel marker for C-ADM. Further attention should be directed to the detection of rapidly progressive ILD in those patients with anti-CADM-140 autoantibodies.

The assessment and importance of disease activity versus disease damage in patients with inflammatory myopathy

To capture the totality of the effect of a disease on a patient, three aspects of the disease need to be assessed: 1) the disease activity (which is potentially reversible with treatment); 2) damage (defined as irreversible changes in anatomy, physiology, or function) accumulated since the onset of the disease, albeit from the disease itself, comorbid conditions, or as a result of therapy; and 3) the patient's perception of the disease, because this is frequently different from the physician's perception. A fine line exists between under-treating a patient, which may lead to an increase in disease activity, and over- treating a patient, with the risk of serious morbidity from inappropriate therapy. Distinguishing between activity and damage can be difficult and measures to ascertain this are discussed. Further developments are underway to assess the measures that should be used for the assessment of disease activity and damage.

The role of cytokines, chemokines, and adhesion molecules in the pathogenesis of idiopathic inflammatory myopathies

Cytokines, chemokines, and adhesion molecules are important mediators in chronic inflammation and in immune regulation. In idiopathic inflammatory myopathies (IIM), increased expression of proinflammatory cytokines particularly interleukin (IL)-1alpha and IL-1beta, tumor necrosis factor (TNF)-alpha and macrophage inflammatory proteins (MIP)-1alpha, as well as of the inhibitory cytokines transforming growth factor (TGF)-beta was observed in muscle. There was no difference in cytokine and chemokine pattern between polymyositis, dermatomyositis, and inclusion body myositis, which could indicate that similar pathogenetic mechanisms are involved in these subsets of myositis. A prominent finding of IL-1alpha expression in endothelial cells, both in patients with active inflammation and in patients with chronic persisting muscle weakness without inflammation, makes this an interesting molecule in understanding the mechanisms for the pathogenesis of muscle weakness. Involvement of the blood vessels in the pathogenesis of myositis was further supported by increased expression of adhesion molecules and by a phenotypical expression of endothelial cells, resembling high endothelium venules in all three subsets of IIM. The molecular studies to date indicate a role of the microvessels in the pathogenesis of IIM not only in DM, as was previously suggested, but also in PM and IBM. The studies also indicate that IL-1alpha could be a target molecule for new therapeutical interventions.

Aerobic capacity in adult dermatomyositis/polymyositis patients and healthy controls

OBJECTIVE

Assessment of myositis patients has relied on symptoms, strength testing, and serum muscle enzyme activity. Recently, functional assessments and evaluation of strength by dynamometry and of disease activity by magnetic resonance imaging have also been added. Aerobic testing in selected patients has been considered useful.

DESIGN

Case-control study.

SETTING

University Hospital, Vienna, Austria.

PATIENTS

Twenty-two subjects (8 outpatients with chronic dermatomyositis and 3 outpatients with chronic polymyositis, and 11 healthy controls) participated, allowing the identification of 11 case-control pairs matched by age (+/-3 years) and gender (mean age, 48+/-14 yrs; ratio of women to men, 18/4).

MAIN OUTCOME MEASURES

Target parameters were peak oxygen uptake (peak VO2) to estimate aerobic exercise capacity and peak isometric torque for muscle strength. Creatine phosphokinase (CPK) was measured to assess elevation of muscle enzymes.

RESULTS

The mean peak VO2 in patients with dermatomyositis/polymyositis was 15.3 mL/min/kg (SD = 5.8) and in the healthy controls 28.7 mL/min/kg (SD = 7.8). Cardiorespiratory capacity expressed as peak VO2 was thus significantly reduced at 53% (p = .0001) of the control value. Muscle strength expressed as peak isometric torque was significantly lower (p = .01) in patients (mean 148+/-73 Nm) when compared to the control group (mean 261+/-99 Nm). In myositis patients peak VO2 and peak isometric torque correlate well with each other (r = .7631; p = .0001), but not at all with serum CPK levels (r = .056; p = .869).

CONCLUSION

Peak VO2 is significantly diminished in patients with dermatomyositis/polymyositis, compared with age- and sex-matched controls. Serum CPK did not significantly correlate with VO2. Aerobic exercise testing may be a useful assessment parameter in selected patients with dermatomyositis/ polymyositis.

Treatment of inflammatory myopathies

The treatment of the immune-mediated inflammatory myopathies remains largely empirical. Corticosteroids are usually effective in polymyositis and dermatomyositis but may need to be combined with methotrexate or azathioprine in some patients. Intravenous immunoglobulin (IVIg) is effective as add-on therapy in some patients not adequately controlled with steroids or immunosuppressive agents, but further controlled trials of IVIg are necessary to define the indications and optimal dose regimens. Cyclophosphamide, cyclosporin, or chlorambucil may be effective in patients with refractory polymyositis or dermatomyositis. Low-dose whole body or lymphoid irradiation is a last option in severely disabled patients resistant to all other treatments. As a small proportion of patients with inclusion body myositis respond to corticosteroid or immunosuppressive therapy, a 3-6-month trial of such therapy is justified in this condition. More specific immunotherapy for these disorders awaits identification of the target antigens and further clarification of the immunopathogenetic mechanisms.

P-31 magnetic resonance spectroscopy in polymyositis and dermatomyositis. Altered energy utilization during exercise

OBJECTIVE

To explore alterations in energy utilization as a potential etiology for weakness in polymyositis and dermatomyositis (PM/DM).

METHODS

P-31 magnetic resonance spectroscopy studies were performed in patients with acute and treated PM/DM and in normal controls, at rest and with exercise.

RESULTS

Patients with acute and treated PM/DM showed increased ratios of inorganic phosphate to phosphocreatine (PCr) during exercise, with loss of ATP disproportional to loss of PCr.

CONCLUSION

This study demonstrates changes in energy utilization in PM/DM, thus supporting the notion of a metabolic etiology for the weakness associated with these diseases.