Myositis syndromes

A myositis syndrome of myalgia, weakness, stiffness, malaise, and elevations in creatine kinase and aspartate aminotransferase may occur and seems to be more common in patients with renal insufficiency. 

Polymyositis and Dermatomyositis Syndromes Polymyositis and Dermatomyositis Associated with Malignancy Inclusion Body Myositis (IBM)... 

These disorders are all acquired conditions with no evidence of an hereditary basis. Most of them involve inflammation of the skeletal muscle itself (myositis) (Figure 17), though this may sometimes occur because of initial targeting of the muscle vasculature or connective tissue. Many instances of myositis are classed as idiopathic disorders, in that the precise mechanisms of muscle degeneration are not known, but is widely accepted that these syndromes are associated with abnormal function of the immune system. The syndromes of polymyositis (PM) and derma-... 

This form of myositis stands apart from the classical PM/DM syndromes on account of its distinctive clinical and histopathological features. There is no clear difference in incidence between males and females and the disorder is typically one of middle or old age. In the majority of cases, progression is slow and skin involvement is not seen, so that the main question of differential diagnosis is its distinction from chronic PM. Unlike classic PM, weakness involves distal muscles as frequently as proximal muscles. CK levels are usually only moderately raised. A common finding which leads to the correct diagnosis of this condition is its nonresponsiveness to steroid treatment or other forms of immunosuppression. 

Bacterial and viral myositis is well recognized as a clinical entity by muscle pathologists. The viruses most commonly involved appear to be the Coxsackie viruses, the arboviruses, influenza virus, and HIV, but the mechanism whereby the viral infection gives rise to the myositic syndrome is not known. A detailed discussion of such problems is presented later on pages 333-334. 

Complications of influenza may include exacerbation of underlying comorbidities, primary viral pneumonia, secondary bacterial pneumonia or other respiratory illnesses (e.g., sinusitis, bronchitis, otitis), encephalopathy, transverse myelitis, myositis, myocarditis, pericarditis, and Reye s syndrome. 

The sahcylates are useful in the treatment of minor musculoskeletal disorders such as bursitis, synovitis, tendinitis, myositis, and myalgia. They may also be used to relieve fever and headache. They can be used in the treatment of inflammatory disease, such as acute rheumatic fever, rheumatoid arthritis, osteoarthritis, and certain rheumatoid variants, such as ankylosing spondylitis, Reiter s syndrome, and psoriatic arthritis. However, other NS AIDS are usually favored for the treatment of these chronic conditions because of their lower incidence of GI side effects. Aspirin is used in the treatment and prophylaxis of myocardial infarction and ischemic stroke. 

A 24 year old man developed a fever and a generalized maculopapular rash after taking amfebutamone 150 mg bd for 3 weeks (28). Amfebutamone was withdrawn but he went on to develop angioedema, eosinophilia, and a systemic syndrome with hepatitis, myositis, and obstructive lung disease. His symptoms resolved over several weeks with a glucocorticoid. 

Mutations also arise naturally during the manufacture of DNA. Thus, the opportunity for error exists every time a cell replicates. Even so, DNA is correctly made almost always. Predictably, cells that divide numerous times are more at risk for errors than cells that divide less frequently. For example, the egg cells are present in a female at birth and never undergo division, while sperm cells in males are constantly being produced. A theory proposes that the cause of birth defects including a type of dwarfism, Marfan syndrome, and myositis ossificans are typically the result of a defective gene contributed by a mutated sperm. 

Chow LT, Chow WH. Acute compartment syndrome an unusual presentation of gemfibrozil induced myositis. Med J Aust 1993 158(l) 48-9. 

Delayed muscular adverse effects have been occasionally reported including the clinical exacerbation of a latent myopathy (SEDA-19, 336), delayed and severe myopathic changes (313), myositis, polymyositis, and a Lambert-Eaton-like syndrome (SEDA-19, 336) (SEDA-20, 330) (SEDA-22, 403). 

A 300 mg dose of rifabutin is usually well tolerated. Adverse effects include neutropenia, thrombocytopenia, rash, and gastrointestinal disturbances (nausea, flatulence). Myositis (12) and uveitis (13) are rarely observed. The drug-induced lupus-like syndrome has been linked in a few cases with rifampicin and rifabutin. 

Myalgia/Myositis/Myopathy/Myotoxicity (> 1%) Respiratory Flu-like syndrome (< 1%)... 

Connective tissue diseases. Systemic autoimmune rheumatic diseases, including systemic lupus erythematosus, Sjogren syndrome, systemic sclerosis (scleroderma), autoimmune myositis (polymyositis, dermatomyositis), mixed connective tissue disease, and other overlapping syndromes. 

Muscle diseases, autoimmune. Autoimmune diseases associated with profound weakness due to immunological injury of the myofibre ( - myositis, autoimmune) or affecting the neuromuscular junction ( - myasthenia gravis, acquired, Lambert-Eaton myasthenic syndrome). 

A serious side effect or fibrates is a myositis-like syndrome, which is made worse by concurrent use of statins. Such a combination is not recommended except in cases of severe familial hyperlipidaemia. 

UNTOWARD EFFECTS Rifabutin generally is well tolerated in persons with HIV infection primary reasons for discontinuation of therapy include rash (4%), GI intolerance (3%), and neutropenia (2%). Overall, neutropenia occurred in 25% of patients with severe HIV infection who received rifabutin. Uveitis and arthralgias have occurred in patients receiving rifabutin doses >450 mg daily in combination with clarithromycin or fluconazole. Patients should be cautioned to discontinue the drug if visual symptoms occur. Like rifampin, the drug causes an orange-tan discoloration. Rarely, thrombocytopenia, a flu-like syndrome, hemolysis, myositis, chest pain, and hepatitis have occurred. 

Adverse effects. All the hbrates can cause a myositis-like syndrome. Ttie incidence of myositis is increased by concurrent use of HMG CoA inhibilois and such combinations should be avoided. 

Many myositis-specific antibodies are reported in PM/DM, with anti-aminoacyl-tRNA synthetases, the most frequent (Table 3) (223,236). ILD and the presence of anti-synthetase antibodies are strongly associated. Anti-Jo 1 antibodies, which occur most commonly, are found in 30% to 100% of cases with ILD, but in 0% to 37% of other PM/DM patients (28,224,233—235,237—241). The anti-synthetase syndrome (1,2,223,225,236) consists of an association between anti-synthetase antibodies and, in a variable proportion of cases, myositis, fever, arthritis, Raynaud s phenomenon, mechanic s hands, and ILD, which is present in 75% to 89% of cases (28,224,233—235,237—241). The anti-Mi2 antibody, usually found in DM, is also associated with ILD, whereas the anti-SRP antibody is generally not (236). Anti-Jol antibodies are more frequent in PM, whereas non-anti-Jol antibodies are more common in DM, and especially in patients with ILD and CADM (236,242—246). Anti-synthetase antibodies are also reported in IPF (28). 

Myositis-associated antibodies occur also in other CTDs or overlap syndromes (discussed later), which raises nosological issues (Table 3). The anti-Ro/SS-A antibody has been associated with the anti-synthetase syndrome. 

Anti-PM-Scl Peptide complex forming an exosome (exoribonuclease activities) 5-10% In scleroderma, myositis, and scleroderma/ PM-DM overlap syndromes (Caucasians). Sometimes associated with ILD... 

Anti-Ul-RNP Small ribonucleoprotein 5-10% Marker for Sharp s syndrome, also seen in other CTDs and myositis Sometimes associated with ILD... 

Among overlap syndromes, ILD seems to be particularly frequent in patients with sclero(dermato)myositis. Sclero(dermato)myositis differs from MCTD by the absence of features of SLE (327). The anti-PM/Scl antibody is characteristic, although also found in PM, DM, or SSc without feamres of overlap syndromes (328). The reported prevalence of ILD in patients with this antibody is variable, reaching 85% in one series (Fig. 16) (329). Despite the high frequency of ILD, patients with the anti-PM/Scl antibody have a favorable outcome (329). 

PM/DM is an idiopathic inflammatory myopathy however, a number of autoantibody subclassifications correlate with features of clinical disease. When clinical muscle weakness is encountered in the pulmonary clinic, one recent addition to the laboratory armamentarium is the myositis antibody panel. These panels of autoantibody tests can define antibodies to many of the aminoacyl-tRNA synthetases and sometimes help define a CTD when previously not suspected. The most common syndrome is now termed the antisynthetase syndrome when autoantibodies are present in the setting of variable components of fever, myositis, Reynaud s phenomenon, arthritis, mechanic s hands, and ILD (40). Alternative PM/DM diagnostic strategies include targeting muscle weakness with magnetic resonance imaging (MRI) or electromyography (EMG) in preparation for muscle biopsy. It should be noted that some forms of idiopathic myopathy, such as inclusion body myositis, have not been associated with ILD but can present with respiratory impairment due to muscle weakness (41). 

Plastiras SC, Soliotis FC, Vlachoyiannopoulos P, et al. Interstitial lung disease in a patient with anti synthetase syndrome and no myositis. Clin Rheumatol 2007 26(1) 108-111. 

Parissis D, Karkavelas G, Taskos N, Milonas I. (2003) Inclusion body myositis in a patient with a presumed diagnosis of post-polio syndrome. J Neurol 250(5), 619-621. 

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