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Inclusion Body Myositis

Inclusion Body Myositis Causes

Sporadic inclusion body myositis is a rare disease, and its causes are currently unknown. Several researchers have speculated, however, that this condition results from the interaction of a number of genetic and environmental factors. One theory postulates that the inflammation or immune reaction is caused by a viral or autoimmune trigger. This unknown trigger may be the proximal cause of the disease, whereas the degeneration of muscle fibers and protein abnormalities are just secondary reactions. Another theory posits that sIMB is mainly degenerative and is brought about by the aging of the muscle fibers. Advocates of this theory believe that abnormal, potentially pathogenic protein deposits in myofibers are the primary cause of the disease, emphasizing the abnormal accumulation of proteins in cells, the aggregation and misfolding of many proteins, the inhibition of proteosome, and ER (endoplasmic reticulum) stress as causal factors.

Inclusion Body Myositis Definition

Sporadic inclusion body myositis (acronym: sIBM) is a rare condition marked by gradually progressive wasting and weakness of the proximal and distal muscles. This inflammatory muscle disease is most evident in the muscles of the legs and arms. Two progressive processes, one degenerative and the other autoimmune, seem to occur simultaneously in the muscle cells. In the autoimmune aspect, the T cells are cloned, seemingly driven by certain antigens to invade the fibers of the muscles. In the degeneration aspect, holes (vacuoles) appear in the muscle, with amyloid-related protein deposits and abnormal filamentous inclusions appearing in the cells.

Inclusion Body Myositis Diagnosis

A diagnosis for inclusion body myositis is based primarily on clinical signs and consequent testing. The initial clinical signs are the evident symptoms -- tripping, falling down, finger flexion weakness, inability to grip objects, etc. In addition, a variable of tests can help in diagnosing the disease, including a blood test to screen for CK (creatine kinase) levels. CK is a blood enzyme that is produced when muscle cells are damaged. Elevated CK levels thus indicate abnormal muscle damage. Meanwhile, an EMG (electromyography) can be done to identify characteristic abnormalities. The best diagnostic tool, however, is a muscle biopsy, wherein a small sample of the muscle is surgically removed for laboratory analysis.

Inclusion Body Myositis Symptoms and Signs

Symptoms of sporadic inclusion body myositis vary greatly, depending on the age when the condition first presents. In general, sIBM presents as progressive weakening of the muscles. The quadriceps muscles of the thighs and the arm muscles that control finger flexing are affected in the early stages. Other early signs of sIBM include falling or tripping, trouble climbing a flight of stairs, difficulty manipulating the fingers, inability to turn doorknobs, etc. As the illness progresses, the mobility of patients becomes even more restricted. In later stages, patients may be unable to bend down, reach for or grab objects, walk briskly, and so on. Several cases have noted complaints of loss of balance. This is most likely because the patient's muscles become unable to compensate for an off-balanced posture. Since sIBM results in leg muscle weakness and instability, patients have a high risk of serious injury from tripping or falling down. Additionally, severe muscle pain is a common symptom.

Inclusion Body Myositis Treatment

To date, several clinical trials have been done to treat inclusion body myositis. While a few results have shown short-term improvements in patients, no medication has demonstrated any long-term efficacy. Currently, biologic agents, a new mode of sIBM treatment, are being researched in relation to immune disorders. Another study is currently in the works to use Campath to treat this form of myositis.

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