Treatment and investigation of idiopathic inflammatory myopathies

Clinical and radiological features of lung disorders related to connective-tissue diseases: a pictorial essay

Connective tissue diseases (CTDs) include a spectrum of disorders that affect the connective tissue of the human body; they include autoimmune disorders characterized by immune-mediated chronic inflammation and the development of fibrosis. Lung involvement can be misdiagnosed, since pulmonary alterations preceded osteo-articular manifestations only in 20% of cases and they have no clear clinical findings in the early phases. All pulmonary structures may be interested: pulmonary interstitium, airways, pleura and respiratory muscles. Among these autoimmune disorders, rheumatoid arthritis (RA) is characterized by usual interstitial pneumonia (UIP), pulmonary nodules and airway disease with air-trapping, whereas non-specific interstitial pneumonia (NSIP), pulmonary hypertension and esophageal dilatation are frequently revealed in systemic sclerosis (SSc). NSIP and organizing pneumonia (OP) may be found in patients having polymyositis (PM) and dermatomyositis (DM); in some cases, perilobular consolidations and reverse halo-sign areas may be observed. Systemic lupus erythematosus (SLE) is characterized by serositis, acute lupus pneumonitis and alveolar hemorrhage. In the Sjögren syndrome (SS), the most frequent pattern encountered on HRCT images is represented by NSIP; UIP and lymphocytic interstitial pneumonia (LIP) are reported with a lower frequency. Finally, fibrotic NSIP may be the interstitial disease observed in patients having mixed connective tissue diseases (MCTD). This pictorial review therefore aims to provide clinical features and imaging findings associated with autoimmune CTDs, in order to help radiologists, pneumologists and rheumatologists in their diagnoses and management.

Rituximab for Inflammatory Myopathies in a Colombian Cohort

INTRODUCTION/OBJECTIVES

Rituximab (RTX) is a treatment for refractory inflammatory myopathies, such as dermatomyositis (DM) and polymyositis (PM). This study describes the characteristics of patients receiving RTX for myositis in our institution to evaluate its efficacy.

METHOD

We collected demographic data from all patients diagnosed with DM or PM who received RTX between 2011 and 2018. Clinical and serological variables (including creatine phosphokinase [CPK] levels) were analyzed. Remission of disease was defined as no evidence of disease activity (active myositis) for longer than a 6-month continuous period while undergoing myositis therapy or no medication.

RESULTS

Eighteen patients who had received first-line immunosuppressants were included. Fifteen (83%) had DM, 2 (11%) had PM, 1 had juvenile dermatomyositis, and 14 (77%) were women. All patients received glucocorticoids. Three patients (16.6%) were treated with RTX as monotherapy, and 15 (83.3%) were treated with RTX combined with other immunosuppressants. On average, there were 2 RTX treatment cycles. Improved muscular weakness was found in 13 cases (72%), and improved serum CPK levels were found in 15 cases (83%). Twelve patients (66%) achieved remission.

CONCLUSIONS

Most patients experienced an objective improvement, as reflected in their serum CPK values and degree of muscular weakness. This suggests that RTX could be helpful in treating refractory myositis.

Antimalarial drugs-are they beneficial in rheumatic and viral diseases?-considerations in COVID-19 pandemic

The majority of the medical fraternity is continuously involved in finding new therapeutic schemes, including antimalarial medications (AMDs), which can be useful in combating the 2019-nCoV: coronavirus disease (COVID-19). For many decades, AMDs have been widely used in the treatment of malaria and various other anti-inflammatory diseases, particularly to treat autoimmune disorders of the connective tissue. The review comprises in vitro and in vivo studies, original studies, clinical trials, and consensus reports for the analysis, which were available in medical databases (e.g., PubMed). This manuscript summarizes the current knowledge about chloroquine (CQ)/hydroxychloroquine (HCQ) and shows the difference between their use, activity, recommendation, doses, and adverse effects on two groups of patients: those with rheumatic and viral diseases (including COVID-19). In the case of connective tissue disorders, AMDs are prescribed for a prolonged duration in small doses, and their effect is observed after few weeks, whereas in the case of viral infections, they are prescribed in larger doses for a short duration to achieve a quick saturation effect. In rheumatic diseases, AMDs are well tolerated, and their side effects are rare. However, in some viral diseases, the effect of AMDs is questionable or not so noticeable as suggested during the initial prognosis. They are mainly used as an additive therapy to antiviral drugs, but recent studies have shown that AMDs can diminish the efficacy of some antiviral drugs and may cause respiratory, kidney, liver, and cardiac complications.

Treatment of inflammatory myopathies

INTRODUCTION

The idiopathic inflammatory myopathies (IIM) dermatomyositis (DM) and polymyositis (PM) are chronic diseases affecting the striated muscles with variable involvement of other organs. Glucocorticoids are considered the cornerstone of treatment, but some patients require adjunctive immunosuppressive agents because of insufficient response to glucocorticoids, flares upon glucocorticoid tapering, or glucocorticoid-related adverse events. Areas covered: The aim of this article was to review (PubMed search until February 2018) the evidence on established and new therapies derived from randomized controlled trials (RCTs) on adult DM and PM. In addition, key data from open-label trials, case reports, and abstracts were included where data from RCT were lacking. Expert commentary: Numerous synthetic and biological immunosuppressive agents are currently available to treat the IIM, sometimes in combination. The choice of the specific medication in the individual patient depends upon the disease phenotype and patient's characteristics. Exercise improves muscle performance without causing disease flares and should be an integral part of the treatment of the IIM. Prompt diagnosis and treatment can lead to better outcome.

Hypercapnic respiratory failure during pregnancy due to polymyositis-related respiratory muscle weakness: a case report

Background

Polymyositis is a rare medical disorder complicating pregnancy. Ventilatory muscle weakness leading to respiratory failure is an uncommon manifestation of this autoimmune disease. We report a case of life-threatening hypercapnic respiratory failure due to polymyositis-related respiratory muscle weakness in a pregnant woman.

Case presentation

A 31-year-old, African woman in her second trimester of pregnancy presented to the emergency department with fever, shortness of breath and muscle weakness. Initial investigations excluded pulmonary infection, thromboembolism, and cardiac dysfunction as the underlying cause of her symptoms. She developed deterioration in her level of consciousness due to carbon dioxide narcosis requiring invasive mechanical ventilation. Further workup revealed markedly elevated serum creatine kinase, abnormal electromyography and edema of her thigh muscles on magnetic resonance imaging. Diagnosis of polymyositis was confirmed by muscle biopsy. After receiving pulse steroid, intravenous immunoglobulins, and maintenance immunosuppressive therapy, our patient’s respiratory muscle function improved and she was weaned off mechanical ventilation. Despite good maternal recovery from critical illness, the fetus developed intrauterine growth retardation and distress necessitating emergency cesarian section.

Conclusions

New-onset polymyositis during pregnancy presenting with respiratory failure is rare. Early diagnosis and prompt initiation of therapy is necessary to improve fetal and maternal outcomes.

Medical resource utilization in dermatomyositis/polymyositis patients treated with repository corticotropin injection, intravenous immunoglobulin, and/or rituximab

Background

Dermatomyositis and polymyositis (DM/PM) are rare, incurable inflammatory diseases that cause progressive muscle weakness and can be associated with increased medical resource use (MRU). When corticosteroid treatment is unsuccessful, patients may receive intravenous immunoglobulin (IVIg), rituximab, or repository corticotropin injection (RCI). This study compared real-world, non-medication MRU between patients treated with RCI and those treated with IVIg and/or rituximab for DM/PM.

Methods

Claims of DM/PM patients were analyzed from the combination of three commercial health insurance databases in the United States from July 2009 to June 2014. Patients treated with RCI were propensity score matched to those treated with IVIg, rituximab, and both (IVIg+rituximab) based on demographics, prior clinical characteristics, and prior MRU. Per-patient per-month (PPPM) MRU and costs were compared using Poisson regression and generalized linear modeling, respectively.

Results

One-hundred thirty-two RCI, 1,150 IVIg, and 562 rituximab patients had an average age of 52.6, 46.6, and 51.7 years, respectively, and roughly two-thirds were female. After matching, there were no significant differences in demographics or prior clinical characteristics. RCI patients had fewer PPPM hospitalizations (0.09 vs 0.17; P=0.049), shorter length of stay (LOS; 3.24 days vs 4.55 days; P=0.004), PPPM hospital outpatient department (HOPD) visits (0.60 vs 1.39; P<0.001), and PPPM physician office visits (2.01 vs 2.33; P=0.035) than IVIg. RCI had fewer PPPM HOPD visits (0.56 vs 0.92; P<0.001) than rituximab. Patients treated with RCI had shorter LOS (2.18 days vs 5.15; P<0.001) and less PPPM HOPD visits (0.53 vs 1.26; P<0.001) than IVIg+rituximab. Total non-medication PPPM costs were 23%–75% lower for RCI compared to IVIg ($2,126 vs $3,964; P<0.001), rituximab ($2,008 vs $2,607; P=0.018), and IVIg+rituximab ($1,234 vs $4,858; P<0.001).

Conclusion

Patients treated with RCI had less PPPM non-medication MRU and costs than those treated with IVIg and/or rituximab, particularly in the hospital setting where significant costs are incurred.

Idiopathic inflammatory myopathies

Inflammatory myopathies are chronic, immune-mediated diseases characterised by progressive proximal muscle weakness. They encompass a variety of syndromes with protean manifestations. The diagnosis is based on Bohan and Peter's classification criteria, which nowadays seem to be obsolete. Our increasing knowledge about the risk factors, genetic susceptibility and immunological pathways in the disease mechanism leads to the establishment of a new, immunogenetically and serologically validated diagnostic criteria system. The treatment of idiopathic inflammatory myopathy is also a complex task requiring much experience. The aims of therapy are to increase muscle strength, prevent the development of contractures and manage the systemic manifestations of the disease. The most important one is the early detection of diseases and patients' immunological control in special centres. Using the basis therapeutic drugs temporary or permanent remission can be achieved, which improves patientsG' quality of life and functional ability. Rehabilitation and physiotherapy in the remission period may significantly improve the outcome of patients with functional disorders. The introduction of new biological therapies further allows us to control the myositis patients' state more effectively. The aim of this review is to summarise our knowledge about clinical symptoms, pathomechanism, as well as genetic, serologic and environmental risk factors. We would also like to present the way to diagnosis and the latest research about diagnostic criteria system, proposed outcome measures and therapeutic possibilities.

Medical costs and health-care resource use in patients with inflammatory myopathies in an insured population

INTRODUCTION

In this study we determined the health-care costs and resource utilization associated with idiopathic inflammatory myopathies (IIMs) in a large managed care plan in the USA.

METHODS

Myositis subjects ≥18 years of age with claims-based evidence of IIMs were identified from a health plan database. Subjects were matched with unaffected controls, and costs and resource use were determined during a 12-month period.

RESULTS

A total of 1781 newly diagnosed IIM subjects were matched to 5343 controls, and 2697 subjects with existing disease were matched to 8091 controls. Mean overall annual medical costs were higher among newly diagnosed subjects ($16,319 vs. $4926, P < 0.001) and subjects with an existing IIM ($15,539 vs. $5210, P < 0.001) in comparison to controls. IIM subjects had significantly higher mean counts of ambulatory visits, specialist visits, and inpatient hospital stays compared with controls (all P < 0.001).

CONCLUSION

Our analysis suggests that IIMs have increased medical costs and resource use.

Isolated necrotizing myopathy associated with ANTI-PL12 antibody

INTRODUCTION

Immune-mediated myopathies are a heterogeneous group of chronic autoimmune disorders. Autoantibodies associated with this disease complex are classified into myositis-associated and myositis-specific. Anti-tRNA synthetase antibodies are the most well known of the myositis-specific antibodies. Previous reports have revealed an association of tRNA synthetase autoantibodies with systemic connective tissue disorders.

METHODS

Our case report involved a 49-year-old man who developed difficulty walking and climbing stairs 5 months prior to his initial visit. No rash or skin changes were observed.

RESULTS

Laboratory testing was positive for anti-PL12 autoantibody with a negative evaluation for connective tissue disorder (CTD). The patient was found to have necrotizing myopathy associated with anti-PL12 antibodies in the absence of inflammatory changes on biopsy, significant derangement of muscle enzymes, or findings characteristic of a typical CTD.

CONCLUSION

A high index of suspicion must be maintained for immune-mediated necrotizing myopathy despite the absence of an identifiable CTD and milder symptoms.

Telomere length and regulatory proteins in human skeletal muscle with and without ongoing regenerative cycles

New insights suggest the existence of telomere regulatory mechanisms in several adult tissues. In this study, we aimed to assess in vivo telomere length and the presence of specific proteins involved in telomere regulation in a model of human skeletal muscle with (patients with dermatomyosis or polymyositis) and without ongoing regenerative events (healthy subjects). Mean (meanTRF) and minimal telomere (miniTRF) lengths and the expression of telomerase, tankyrase 1, TRF2 (telomeric repeat binding factor 2) and POT1 (protection of telomeres 1) were investigated in skeletal muscle samples from 12 patients (MYO) and 13 healthy subjects (CON). There was no significant shortening of telomeres in skeletal muscle from patients compared with control subjects (MYO, meanTRF length 11.0 ± 1.8 kbp and miniTRF length 4.7 ± 0.8 kbp; CON, meanTRF length 10.4 ± 1.1 kbp and miniTRF length 4.6 ± 0.5 kbp). Theoretically, telomere length can be controlled by endogenous mechanisms. Here, we show for the first time that expression levels of telomerase, tankyrase 1, TRF2 and POT1 were, respectively, six-, seven-, three- and fivefold higher in the nuclear fraction of skeletal muscle of MYO compared with CON (P < 0.05). This suggests the existence of endogenous mechanisms allowing for telomere regulation in skeletal muscle with ongoing cycles of degeneration and regeneration and a model where regulatory factors are possibly involved in the protection of skeletal muscle telomeres.

Trichinella inflammatory myopathy: host or parasite strategy?

The parasitic nematode Trichinella has a special relation with muscle, because of its unique intracellular localization in the skeletal muscle cell, completely devoted in morphology and biochemistry to become the parasite protective niche, otherwise called the nurse cell. The long-lasting muscle infection of Trichinella exhibits a strong interplay with the host immune response, mainly characterized by a Th2 phenotype.

The aim of this review is to illustrate the role of the Th2 host immune response at the muscle level during trichinellosis in different experimental models, such as knock-out or immuno-modulated mice. In particular, in knock-out mice a crucial role of IL-10 is evident for the regulation of inflammation intensity.

The muscular host immune response to Trichinella is partially regulated by the intestinal phase of the parasite which emphasizes the intensity of the following muscle inflammation compared with animals infected by synchronized injections of newborn larvae. In eosinophil-ablated mice such as PHIL and GATA-- animals it was observed that there was an increased NOS2 expression in macrophages, driven by higher IFN-γ release, thus responsible for muscle larva damage.

Besides modulation of the intestinal stage of the infection, using recombinant IL-12, increases the muscular parasite burden delaying adult worm expulsion from the intestine. Furthermore, a Th1 adjuvant of bacterial origin called Helicobacter pylori neutrophil activating protein (HP-NAP), administered during the intestinal phase of trichinellosis, alters the Th2 dependent response at muscle level.

All these data from the literature delineate then a mutual adaptation between parasite and host immune response in order to achieve a strategic compromise between two evolutionary forces pointed towards the survival of both species.

Nonimmune mechanisms of muscle damage in myositis: role of the endoplasmic reticulum stress response and autophagy in the disease pathogenesis

PURPOSE OF REVIEW

Recent literature in inflammatory myopathies suggests that both immune (cell-mediated and humoral) and nonimmune [endoplasmic reticulum (ER) stress and autophagy] mechanisms play a role in muscle fiber damage and dysfunction. This review describes these findings and discusses their relevance to disease pathogenesis and therapy.

RECENT FINDINGS

Recent studies highlight the role of ER stress response, especially the roles of hexose-6-phosphate dehydrogenase and ER-anchored RING finger E3 ligase in the activation of unfolded protein response and the formation of vacuoles and inclusions in myopathies. Several studies investigated the link between inflammation and the beta-amyloid-associated muscle fiber degeneration and loss of muscle function. Likewise, the roles of ER stress and autophagy in skeletal muscle damage have been explored in multiple muscle diseases.

SUMMARY

Current data indicate that the ER stress, nuclear factor-kappaB pathway and autophagy are active in the skeletal muscle of myositis patients, and the proinflammatory nuclear factor-kappaB pathway connects the immune and nonimmune pathways of muscle damage. The relative contributions of each of these pathways to muscle fiber damage are currently unclear. Therefore, further defining the role of these pathways in disease pathogenesis should help to design effective therapeutic agents for these diseases.

National registry of patients with juvenile idiopathic inflammatory myopathies in Hungary—Clinical characteristics and disease course of 44 patients with juvenile dermatomyositis

Idiopathic inflammatory myopathies (IIMs) are systemic autoimmune diseases characterized by chronic muscle inflammation resulting in progressive weakness and frequent involvement of internal organs, mainly the pulmonary, gastrointestinal and cardiac systems which considerably contribute to the morbidity and mortality of the IIMs. Aim of this study was to present clinical characteristics, disease course, frequency of relapses and survival in patients with juvenile dermatomyositis (DM). A national registry of patients with juvenile IIMs was elaborated by the authors in Hungary. We have summarized data of the register according to signs and symptoms, disease course, frequency of relapses and survival of patients with juvenile IIM. Analysis was performed using data of 44 patients with juvenile DM diagnosed between 1976 and 2004 according to Bohan and Peter's criteria. Survival probability was calculated by Kaplan-Meier method. Data of patients with juvenile DM were compared with data of 66 patients with adult DM. The most frequent cutaneous features were facial erythema and heliotrope rash. Extramuscular and extraskeletal manifestations of the disease were more frequent in adult patients. The most common extramuscular feature was arthralgia in both groups of patients with juvenile or adult DM. Cardiac manifestation of the disease was not observed in juvenile patients. Respiratory muscle involvement and interstitial lung disease (ILD) were more frequent among adult DM patients than cardiac manifestation of the myositis. In view of the disease course, the authors found that frequency of polycyclic and monophasic subtypes of the disease were mainly similar. The hazard of relapse was found higher during the first year after the remission. None of the juvenile patients died. Among adult patients four disease-specific deaths occurred. There was no correlation between relapse free survival and initial therapeutic regimen. Many of our patients had polycyclic or chronic disease. As relapses can occur after a prolonged disease-free interval, patients should be followed up for at least 2 years. Although we found favourable survival probability, further investigations are needed to assess functional outcome.

Anti-Jo-1 antibody positive polymyositis—successful therapy with leflunomide

Idiopathic inflammatory myopathies (IM), including dermatomyositis (DM) and polymyositis (PM), are a group of systemic rheumatologic diseases of unknown etiology characterized by chronic myositis. Antisynthetase antibodies such as the anti-Jo-1 antibody are known to be highly specific for inflammatory myopathies. Patients with this antibody frequently show a combination of symptoms including interstitial lung disease, fever, polyarthritis, myositis, Raynaud's phenomenon and "mechanic's hands". In the management of PM with anti-Jo-1 antibody, immunosuppressive agents are used to control the disease. Leflunomide is a new immunosuppressive drug recently introduced in the treatment of rheumatoid and psoriatic arthritis. Here, we report two cases of female patients with PM and anti-Jo-1 antibodies, who were successfully treated with leflunomide.

Predictability of the clinical course of juvenile dermatomyositis based on initial muscle biopsy: A retrospective study of 72 patients

OBJECTIVE

Except when the diagnosis of juvenile dermatomyositis (DM) is in doubt, a case has not been made for routine muscle biopsy (MB). We sought to determine whether MB findings prior to systemic therapy have prognostic value.

METHODS

We reviewed the hospital records and slides prepared from the initial open MB of 72 patients treated at one center between 1977 and 2002 and followed for a minimum of 2 years. None of the patients had received a course of systemic corticosteroid therapy at the time of MB. Our approach to MB evaluation was based on recent discussions with muscle pathology experts to develop criteria for assessing inflammation, vasculopathy, myofiber atrophy, regeneration, acute and chronic myopathic change, and stromal changes. Using simple and multivariate logistic regression, we tested each MB parameter for ability to predict outcome using 2 published classification systems.

RESULTS

Extensive active myopathic changes (excluding regeneration) and central nuclei without basophilia predicted chronic juvenile DM. Severe arteropathic change, positive arterial direct immunofluorescence, obvious foci of severe capillary loss/endomysial fibrosis, and muscle infarcts predicted chronic juvenile DM, particularly with ulceration. Other MB parameters, regardless of severity, were not significant predictors of chronic juvenile DM versus limited disease.

CONCLUSION

A scoring system for evaluating pretreatment MB in juvenile DM that focuses on extent of necrotizing myopathy, severity of vasculopathy, and features of established chronicity such as central nucleation of nonbasophilic myofibers may provide a basis for stratification of therapeutic regimens according to risk for chronic disease. The validity of our findings should be prospectively tested.

Novel aspects on the contribution of T cells and dendritic cells in the pathogenesis of myositis

This review focuses on recent advances and new hypothesis in the understanding of the T and dendritic cells contribution to the pathogenesis of idiopathic inflammatory myopathies (IIMs), especially polymyositis (PM) and dermatomyositis (DM). The new data show that non-specific amplification of muscle inflammation by T lymphocyte and dendritic cells may result from the local production of cytokines and chemokines. Synergistic interactions between these factors explain some of the clinical features. The potent role of these molecules suggests their potential for therapeutic manipulation using specific inhibitors.

Polymyositis—a further investigation

In essence, this paper describes the model-based interpretation of measurements in order to gain insight into physiological processes. The paper extends the mathematical model developed previously to control and monitor a polymyositis patient. The extension considers two further yet different types of muscle attack. The model is applied to simulate, first, the total serum creatine kinase levels, which then are matched to the observed values. The outcomes of this approach yield considerable information about the reactions taking place including various concentration levels over time such as prednisolone. The changes in the muscle attack are estimated. Examples illustrate how the model may be used to assess, for a single patient, the maximum reduction of the muscle attack whilst keeping the prednisolone concentration as low as possible. The model has been successfully used to interpret variations in daily heart rate measurements of a polymyositis patient. Consequently, it is shown how daily heart rate measurements may now be used to complement the control and monitoring of the polymyositis patient. The model is used to explore multi-patient statistics. It shows the dangers of using such an approach. The model illustrates the need for longitudinal studies.

Inflammatory myopathies: clinical, diagnostic and therapeutic aspects

The three major forms of immune-mediated inflammatory myopathy are dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM). They each have distinctive clinical and histopathologic features that allow the clinician to reach a specific diagnosis in most cases. Magnetic resonance imaging is sometimes helpful, particularly if the diagnosis of IBM is suspected but has not been formally evaluated. Myositis-specific antibodies are not helpful diagnostically but may be of prognostic value; most antibodies have low sensitivity. Muscle biopsy is mandatory to confirm the diagnosis of an inflammatory myopathy and to allow unusual varieties such as eosinophilic, granulomatous, and parasitic myositis, and macrophagic myofasciitis, to be recognized. The treatment of the inflammatory myopathies remains largely empirical and relies upon the use of corticosteroids, immunosuppressive agents, and intravenous immunoglobulin, all of which have nonselective effects on the immune system. Further controlled clinical trials are required to evaluate the relative efficacy of the available therapeutic modalities particularly in combinations, and of newer immunosuppressive agents (mycophenolate mofetil and tacrolimus) and cytokine-based therapies for the treatment of resistant cases of DM, PM, and IBM. Improved understanding of the molecular mechanisms of muscle injury in the inflammatory myopathies should lead to the development of more specific forms of immunotherapy for these conditions.

Controlling and monitoring polymyositis under steroid therapy

This paper illustrates how considerable information may be extracted from the easily obtained serum creatine kinase levels as a function of prednisolone intake in controlling and monitoring polymyositis effectively. A simple process is developed to enable a clinician to determine readily the optimum prednisolone intake to give the minimum average steroid levels within the patient with an effective reduction in the muscle damage arising from the polymyositis. As part of the process it is demonstrated how the effect of other drugs or natural products may be ascertained and monitored. The effects of specific Mannatech products are detailed as an example.

Inflammatory myopathies

Inflammatory myopathies are the result of infiltration of inflammatory cells into striated muscle, with or without an association with an underlying cause. Two broad classifications are IIMs and secondary inflammatory myopathies associated with other diseases. Standard diagnostic criteria for inflammatory myopathy include the presence of weakness or loss of specific muscle group function, an increase in CK, EMG changes associated with muscle membrane instability, and histologic evidence of inflammation. Not all these criteria, however, must be present. Fresh-frozen biopsy from two proximal muscles is recommended for biopsy confirmation. IIM can either focally affect head or neck muscles or be more diffuse. MMM is an immune-mediated disease characterized by a humoral antibody produced against the unique type IIM and type I variant mvofibers of masticatory muscles of dogs, which causes inflammation and loss of function of the muscles of mastication. Idiopathic polymyositis can affect focal muscle groups (extraocular, laryngeal) or present as multifocal or diffuse involvement of skeletal muscle in the cat and dog. Familial canine DM is an inflammatory disease of the striated muscle, skin, and vasculature in young Collies, Shetland Sheepdogs (Shelties), and, rarely, Collie-crossbred dogs. Immunosuppressive therapy is the key to successful treatment. Protozoal parasitic myopathies are the most common cause of clinically relevant secondary inflammatory myopathies. The degree of systemic involvement is often the limiting factor to successful treatment. Early recognition of the clinical signs for proper diagnostic testing and institution of appropriate therapy can result in a rewarding outcome in treating inflammatory myopathies in the cat and dog.

Oxides and apoptosis in inflammatory myopathies

Reactive oxygen intermediates (ROI) and nitric oxide (NO(.)) are produced in abundance in the inflammatory muscle diseases of autoimmune origin polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). However, their role in the pathogenesis of these diseases is so far not clear. In contrast to demyelinating neuropathies, there is no convincing evidence for oxide-induced apoptosis either in myocytes or in lymphocytes and phagocytes in inflammatory myopathies. On the contrary, NO(.) released at low concentrations at target sites may even have cell-protective effects. A major mechanism of protection from apoptosis in both myocytes and inflammatory cells seems to be the upregulation of anti-apoptotic proteins like Bcl-2. Caution is warranted to apply antioxidative and anti-apoptotic agents to patients with inflammatory myopathies as long as the pathogenic role of oxides and apoptosis in the individual case is not resolved.

Recent advances in the management of adult myositis

Standard drug therapy of adult polymyositis, dermatomyositis and inclusion body myositis includes high-dose corticosteroids and cytotoxic drugs (methotrexate, azathioprine (AZA) and cyclophosphamide). Recent data are in favour of the early introduction of a cytotoxic or immunomodulating drug in addition to corticosteroid therapy. In patients with corticosteroid- and cytotoxic-resistant myositis, promising novel approaches to management include: iv. megadose pulse methylprednisolone combined with cytotoxic drugs, combination therapy with both methotrexate and AZA, cyclosporin, tacrolimus, fludarabine and iv. immunoglobulin (IVIG). Recent advances in the understanding of the role of cytokines and complement, in the pathogenesis of myositis, have led to preliminary therapeutic trials of three biological agents: etanercept, infliximab and anti-C5 monoclonal antibody.

An insight into cortisol and polymyositis control with steroid therapy

In the present report we have developed a mathematical model to describe the processes involved during high steroid therapy. We have shown that the model can predict clinical observations as well as determine the optimum steroid regimen without relying on trial and error methods. The model incorporates rate processes that simplify the physiological complexity as a few representative steps. In this way, it is possible to simulate clinical observations and then to predict clinical outcomes due to drug concentrations or additional reactions within the body. Specific examples are provided from patients with polymyositis and Becker's disease. For the first time, we provide an explanation into the control of cortisol production, and determine an optimum prednisolone concentration in order to minimize steroid side effects while maintaining adequate control of muscle degradation.