Necrotizing autoimmune myopathy
What is it?
Necrotizing myopathy can also be referred to as necrotizing autoimmune myopathy (NAM) or immune-mediated necrotizing myopathy (IMNM). The condition is characterized by signs of necrosis, or cell death, in the muscles, which causes weakness and fatigue. As with other types of myositis, there is no known cause or cure for necrotizing myopathy. However, treatments are available that can successfully manage symptoms.
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Necrotizing autoimmune myopathy.
Signs & symptoms
Like other forms of myositis, patients with necrotizing myopathy may experience the following symptoms:
* Weakness in the muscles closest to the center of the body, such as the forearms, thighs, hips, shoulders, neck, and back
* Difficulty climbing stairs and standing up from a chair
* Difficulty lifting arms over the head
* Falling and difficulty getting up from a fall
* A general feeling of tiredness
Diagnosis
Due to the rarity of immune-mediated necrotizing myopathy (IMNM), diagnosis and treatment are usually managed by a specialty center with experience in diagnosing and treating inflammatory myopathies and may include rheumatologists, neurologists, and neuromuscular specialists. This may be in coordination with a primary care physician (PCP). Consultation with other specialists may be required depending on your symptoms, other coexisting illnesses, and other organ involvement and may include: cardiologist, pulmonologist, oncologist, endocrinologist, and pain management. Exercise is important for myositis patients. Therefore, you may also see a physical therapist, occupational therapist, and, if you have trouble swallowing (dysphagia), you may also see a speech-language pathologist.
Clinical and Physical Exam- A complete medical and family history is important in helping to diagnosis a rare and complex disease such as IMNM. We suggest writing a detailed medical and family history that you can share with your medical team and that can be used for all future appointments.The physical exam and complete medication history are also very important.
Blood Testing- Your doctor will likely order various blood tests when suspecting IMNM in order to measure autoimmune and inflammatory markers and to check for myositis-specific and myositis-associated antibodies, cancer markers, and other antibodies.
EMG and Nerve Conduction Study (NCS)- An EMG (Electromyography) is a test that checks the health of the muscles and the nerves that control the muscles. With IMNM, the EMG may show an irritable myopathy pattern as with other inflammatory myopathies. EMG testing can help distinguish between weakness due to muscle disease from weakness due to nerve problems. Nerve conduction study is usually done during the same visit and is a test to see how fast electrical signals move through a nerve.
MRI (Magnetic Resonance Imaging)- MRI is being used more frequently and can show changes suggesting muscle inflammation. Physicians may also use MRI to choose the best muscle for biopsy.
Muscle Biopsy- The muscle biopsy is important for a diagnosis of IMNM, especially when the antibodies (HMGCR and SRP) are negative. A doctor will remove a small piece of muscle tissue, either via a needle biopsy or an open surgical biopsy, and send it to a lab for testing. An open muscle biopsy is typically done as an outpatient procedure, however the exact plan will be determined by you and your doctors.
Your doctor will choose the weakest muscle, careful to avoid the site of any recent EMG, for biopsy. An MRI can be helpful in locating the best muscle to biopsy.
Treatment
Such as with statins, it was once thought that discontinuing the offending drug would eliminate symptoms of IMNM within weeks or months. However, in recent years it has become recognized that some patients who discontinue the drug do not get better or improve because in these patients there is an autoimmune process involved.
There are no FDA approved therapies for IMNM or any of the inflammatory myopathies.
Patients use off-label medications with very little science behind them. These are a few standard medications used to treat many other autoimmune diseases with the most common being immunosuppressive medications.
Patients may start to see improvement after several weeks of high-dose corticosteroids. The physician will likely conduct a follow up with both a physical exam to determine if muscle strength has improved as well as another CK/CPK blood test to check to see if the levels have decreased.
The goals of treatment for IMNM are to eliminate or reduce inflammation, restore muscle performance and strength, reduce morbidity, and improve a patient’s quality of life.
There are no FDA approved therapies for IMNM, aside from steroids, which is a standard treatment for inflammatory myopathies, and which are not recommended for long-term use.
Finding a combination of medications is often needed for successful treatment.
☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.
Learn more about our editorial process for content accuracy.
Source of Information - We analyze big data of more than 23 million patients de-identified medical records from the following sources:
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