Muscle Disorders
Myositis
Causes
Myositis means inflammation of the muscles that you use to move your body. An injury, infection, or autoimmune disease can cause it.
Signs and Symptoms
· Muscle weakness, sometimes with muscle pain
· General tiredness and fatigue
· Trouble climbing stairs, standing from a seated position, or reaching up
· Difficulty swallowing or breathing
· Rash on knuckles, chest, face and back
· Persistent dry cough
Diagnosis
A doctor may suspect myositis based on a person’s symptoms of muscle weakness or other evidence of myositis. Tests for myositis include:
· Blood tests
· MRI scan: an MRI scan can help identify areas of myositis and changes in the muscles over time.
· EMG: by inserting needle electrodes into muscles, a doctor can test the response of muscles to electrical nerve signals. EMG can identify muscles that are weak or damaged by myositis.
· Muscle biopsy: this is the most accurate test for diagnosing myositis. A doctor identifies a weak muscle, makes a small incision, and removes a small sample of muscle tissue for testing.
There are many causes of muscle weakness and pain more common than myositis and testing for myositis is not a straightforward process. For these reasons, the process of diagnosing myositis can be long.
Treatment
Myositis treatment varies according to the cause. Inflammatory conditions causing myositis may require treatment with drugs that suppress the immune system, including:
· Prednisone
· Azathioprine (Imuran)
· Methotrexate
Myositis caused by infection is usually due to a virus, and no specific treatment is necessary. Myositis caused by bacteria is uncommon and usually requires antibiotics to prevent life-threatening spread of the infection. Myositis related to a drug is treated by stopping the medication. In cases of myositis caused by statin drugs, muscle inflammation usually subsides within a few weeks after stopping the medicine.
Spinal Muscular Atrophy
Causes
Chromosome 5 SMA is caused by a deficiency of a motor neuron protein called SMN, for “survival of motor neuron.” This protein, as its name implies, seems to be necessary for normal motor neuron function. Its deficiency is caused by genetic flaws (mutations) on chromosome 5 in a gene called SMN1. Neighboring SMN2 genes can in part compensate for nonfunctional SMN1 genes. Other rare forms of SMA (non-chromosome 5) are caused by mutations in genes besides SMN.
Signs and Symptoms
· The primary symptom is weakness of the voluntary muscles.
· The muscles most affected are those closest to the center of the body, such as those of the shoulders, hips, thighs and upper back.
· Special complications occur if the muscles used for breathing and swallowing are affected, resulting in abnormalities in these functions.
· If the muscles of the back weaken, spi...
