Polymyositis - adult

Answer 1

Definition

Polymyositis is a relatively uncommon inflammatory disease that leads to significant muscle weakness.

Causes, incidence, and risk factors

Polymyositis is a skeletal muscle disease also known as idiopathic inflammatory myopathy. The cause of this disorder is unknown. It is thought that an autoimmune reaction or a viral infection of the skeletal muscle may cause the disease.

It can affect people at any age, but most commonly occurs in those between 50 and 70 years old, or in children between 5 and 15 years old. It affects women twice as often as men. It is more common in African-Americans than Caucasians. Overall, about 1 in 100,000 people are diagnosed with some form of inflammatory myopathy each year.

Muscle weaknessmay appear suddenly or occur slowly over weeks or months. The weakness is due to inflammation and the breakdown of the muscles. Patients with this disease may have difficulty raising their arms over the head, rising from a sitting position, or climbing stairs. The voice may be affected through weakness of the throat muscles.

A similar condition, called dermatomyositis, is marked by a dusky, red rash that appears over the face, knuckles, neck, shoulders, upper chest, and back.

Symptoms

Polymyositis is a systemic disease, which means it affects the whole body. Symptoms include:

• Difficulty swallowing
• Muscle pain
• Muscle weakness in the proximal muscles (shoulders, hips, etc.)
• Shortness of breath

Patients may also have morning stiffness, joint pain, fatigue, anorexia, weight loss, and fever.

Signs and tests

• CPK, elevated
• Electromyography
• MRI of affected muscles
• Muscle biopsy
• Serum aldolase, elevated

Treatment

The disease is treated with corticosteroid medications. When an improvement in muscle strength is achieved, usually in 4 to 6 weeks, the medication is slowly tapered off. Maintenance therapy with prednisone may be continued indefinitely. In people who fail to respond to corticosteroids, medications to suppress the immune system may be used.

If the condition is associated with a tumor, the condition may improve if the tumor is removed.

Expectations (prognosis)

Remission (a period when no symptoms are present) and recovery occur in many patients, especially children. For most others, immunosuppressant drugs can control the disease. In adults, death may result from severe and prolonged muscle weakness, malnutrition, pneumonia, or respiratory failure. The major causes of death are cancer (malignancy) and lung disease.

Complications

• Associated cancer (malignancy)
• Calcium deposits in the affected muscles, especially in children with the disease
• Heart disease, lung disease, or abdominal complications

Calling your health care provider

Call your health care provider if you have symptoms of this disorder. Seek emergency treatment if you have shortness of breath and difficulty swallowing.

References

Harris ED, Budd RC, Genovese MC, Firestein GS, Sargent JS, Sledge CB. Kelley's Textbook of Rheumatology. 7th ed. St. Louis, Mo: WB Saunders; 2005:1312-1316.

Goldman L, Ausiello D. Goldman: Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007.

Answer 2

Definition

Polymyositis is a relatively uncommon inflammatory disease that leads to muscle weakness, swelling (inflammation), tenderness, and damage. It is part of a larger group of diseases called myositis.

Causes, incidence, and risk factors

Polymyositis is a skeletal muscle disease that is also known as idiopathic inflammatory myopathy. The cause is unknown. An autoimmune reaction or infection of the skeletal muscle may cause the disease.

Polymyositis can affect people at any age, but it most commonly occurs between ages 50 and 70, or in children ages 5 to 15. It affects women twice as often as men. It is more common in African Americans than Caucasians. Overall, about 1 in 100,000 people are diagnosed with some form of inflammatory myopathy each year.

Other types of inflammatory muscle diseases exist, including inclusion body myositis.

Symptoms

Polymyositis is a systemic disease, which means it affects the whole body. Symptoms include:

• Difficulty swallowing
• Muscle pain
• Muscle weakness in the proximal muscles (shoulders, hips, etc.) that makes it difficult to raise the arms over the head, get up from a sitting position, or climb stairs
• Problems with the voice (caused by weak throat muscles)
• Shortness of breath

Patients may also have:

• Fatigue
• Fever
• Joint pain
• Loss of appetite
• Morning stiffness
• Weight loss

A similar condition called dermatomyositis causes a reddish-purple or red rash on the face or body.

Signs and tests

Muscle weakness and tenderness can be signs of polymyositis. A rash is a sign of a similar condition, dermatomyositis.

Tests may include:

• Autoimmune antibodies and inflammation tests
• CPK
• Electromyography
• MRI of affected muscles
• Muscle biopsy
• Myoglobin in the urine
• Serum aldolase

Patients with this condition must be carefully monitored for cancer.

Treatment

The main treatment is with corticosteroid medications. When muscle strength improves, usually in 4 to 6 weeks, the medication is slowly tapered off. Maintenance therapy with prednisone may be continued indefinitely. In people who fail to respond to corticosteroids, medications to suppress the immune system, such as methotrexate and azathioprine, may be used.

Intravenous gamma globulin has been tried, with mixed results. It is too soon to know what role biologic drugs may play in treating this condition.

If the condition is associated with a tumor, it may improve if the tumor is removed.

Expectations (prognosis)

Response to treatment varies, and it depends on whether there are complications. The 5-year mortality can be as high as 20%.

Many patients, especially children, go into remission (a period when no symptoms are present) and recover. For most other people, immunosuppressant drugs can control the disease.

In adults, death may result from:

• Malnutrition
• Pneumonia
• Respiratory failure
• Severe, long-term muscle weakness

The major causes of death are cancer (malignancy) and lung disease.

Complications

• Calcium deposits in the affected muscles, especially in children with the disease
• Cancer
• Heart disease, lung disease, or abdominal complications

Calling your health care provider

Call your health care provider if you have symptoms of this disorder. Seek emergency treatment if you have shortness of breath and difficulty swallowing.

References

Harris ED, Budd RC, Genovese MC, Firestein GS, Sargent JS, Sledge CB. Kelley's Textbook of Rheumatology. 7th ed. St. Louis, Mo: WB Saunders; 2005:1312-1316.

Goldman L, Ausiello D. Goldman: Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007.

Reviewed By

Review Date: 02/07/2011

Michael E. Makover, MD, professor attending in Rheumatology at the New York University Medical Center, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.