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.

Signs and 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

Disassociated from polymyositis

Necrotizing myopathy is a newly defined form of idiopathic inflammatory myopathy, or myositis. Patients with necrotizing myopathy have muscle biopsies that show much less inflammation in the muscle tissue than polymyositis patients, but they have increased evidence of muscle cell death, or necrosis.

In the past, all patients with muscle weakness, elevated creatine kinase levels in their blood, and other symptoms of myopathy, but who didn’t have skin involvement, were diagnosed with polymyositis. Now, it is recognized that some of these patients have unique findings on their muscle biopsies that distinguish them from those with polymyositis or other forms of myositis.

Categories of necrotizing myopathies

Researchers are also beginning to distinguish different categories of necrotizing myopathy that have different risk factors and different treatments. These distinctions are based on the presence of different autoantibodies in the patient’s blood and most likely indicate that these are different diseases.

Patients with SRP autoantibodies

Anti-signal recognition particle (SRP) autoantibodies appear in the blood tests of many experiencing symptoms of necrotizing myopathy. Patients typically experience sudden and extreme muscle weakness and aches. Some may also have cardiac involvement.

Patients with HMGCR autoantibodies

HMGCR (3-hydroxy-3-methylglutaryl-coenzyme A reductase) is a key enzyme in the production of cholesterol. Patients who have anti-HMGCR antibodies and use statin medications to control high cholesterol may unknowingly develop this type of statin-induced necrotizing myopathy.

All other patients

All other patients with necrotizing myopathy, who do not show SRP or HMGCR autoantibodies in their blood tests are considered by some experts to be included in a separate, third grouping of necrotizing myopathy.

If you are experiencing muscle symptoms involving weakness or fatigue, we encourage you to talk to your doctor to begin the diagnosis process, which includes a muscle biopsy to detect necrosis and various blood tests to detect the presence of autoantibodies. Since necrotizing myopathy is a rare disease, many physicians may not be familiar with the signs and symptoms. If you are  struggling to find an accurate diagnosis, visiting a specialist can help.