Dermatomyositis and polymyositis are autoimmune diseases, meaning that the body’s immune system mistakenly attacks its own healthy cells and tissues. The exact reason why this happens in some people is not fully understood. When the immune system becomes overactive, it can cause inflammation and symptoms such as fatigue, leaving a person feeling extremely tired and run-down, similar to how they might feel when they have the flu.

Myositis can develop on its own or occur alongside other rheumatic diseases. Muscle inflammation may also be associated with conditions such as Sjögren’s syndrome, lupus, and systemic sclerosis, also known as scleroderma.

In a small proportion of people, myositis may be associated with cancer. In some cases, the cancer may trigger an abnormal immune response that contributes to the development of myositis. For this reason, people diagnosed with myositis should undergo appropriate cancer screening based on their age, risk factors, and clinical assessment.

Myositis is best diagnosed by a healthcare professional with experience in identifying and treating the condition. This is usually a rheumatologist, a doctor who specializes in autoimmune diseases and arthritis, or a neurologist, a doctor who specializes in disorders of the nervous system.

The doctor will begin by taking a detailed medical history and performing a thorough physical examination. Based on these findings, additional tests may be ordered to confirm a diagnosis of dermatomyositis or polymyositis and rule out other possible causes of muscle inflammation and weakness.

Other conditions that can cause muscle inflammation or similar symptoms include certain medications and drugs, hormonal imbalances involving the thyroid or adrenal hormones, infections, and rare genetic disorders.

If a diagnosis of dermatomyositis or polymyositis is confirmed, appropriate cancer screening should also be considered, as these conditions can sometimes be associated with an increased risk of cancer.

Blood Tests

Measuring Muscle Enzymes

The first type of blood test measures muscle enzymes in the blood. When muscles become inflamed and damaged, enzymes that are normally found inside muscle cells can leak into the bloodstream. These enzyme levels can then be measured through a blood test.

One of the most commonly measured enzymes is creatine kinase (CK). CK levels are often significantly elevated in people with myositis, sometimes reaching thousands or tens of thousands of units per litre. However, CK levels can be normal in approximately 5% of patients.

Other enzymes that may be elevated include aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and aldolase.

Testing for Autoantibodies

Blood tests can also look for antibodies associated with autoimmune muscle diseases. These include the antinuclear antibody (ANA) test and the extractable nuclear antigen (ENA) panel. Additional myositis-specific and myositis-associated antibody tests may help identify the type of myositis and provide information about associated complications.

Electromyography (EMG)

An electromyography (EMG) test evaluates the electrical activity of muscles and can help identify abnormalities consistent with muscle disease. It can help distinguish myositis from other conditions that cause muscle weakness.

During the procedure, a healthcare professional inserts small, thin needles into selected muscles to record their electrical activity. The results can help determine whether the symptoms are caused by a muscle disorder or another condition affecting the nerves or muscles.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) uses magnetic fields and radio waves to produce detailed images of the muscles. It can help identify areas of muscle inflammation and damage. MRI can also help doctors select an appropriate site for a muscle biopsy.

Muscle Biopsy (Tissue Sample)

A muscle biopsy involves removing a small sample of muscle tissue for examination under a microscope. This is an important diagnostic procedure that can help confirm a diagnosis of dermatomyositis or polymyositis and distinguish these conditions from other muscle disorders.

In people with myositis, the tissue sample may show characteristic patterns of inflammation and muscle damage. The findings are interpreted alongside the patient’s symptoms, physical examination, blood test results, and imaging studies.

Common Tests Used for Cancer Screening

Because certain types of myositis, particularly dermatomyositis, are associated with an increased risk of cancer, appropriate cancer screening is an important part of the diagnostic assessment. The screening approach depends on the patient’s age, sex, type of myositis, risk factors, and other clinical findings.

Patients should inform their doctor if they have a first-degree relative, such as a parent, sibling, or child, who has had cancer, as this information may help guide their assessment.

Depending on the individual circumstances, screening may include:

• CT scans of the chest, abdomen, and pelvis to look for abnormalities that may require further investigation.
• Mammography for breast cancer screening, according to age and individual risk.
• Prostate-specific antigen (PSA) blood testing and, when appropriate, a prostate examination.
• Cervical cancer screening, such as a Pap test or other recommended screening tests.
• CA-125 blood testing, which may be considered in selected circumstances but is not recommended as a routine screening test for ovarian cancer in the general population.
• Colorectal cancer screening, using stool-based tests and/or colonoscopy, as appropriate.
• Thyroid function blood tests and thyroid ultrasound, when clinically indicated.

The specific tests recommended will vary from person to person. Not every patient requires every test listed above, and some investigations are used only when symptoms, examination findings, or individual risk factors suggest they may be helpful.

The exact cause of dermatomyositis and polymyositis is not fully understood. Researchers do not yet know why the immune system mistakenly attacks healthy muscle tissue in some people or why certain individuals develop these conditions while others do not.

In rare cases, dermatomyositis or polymyositis may occur alongside cancer. In some of these cases, the cancer may trigger an abnormal immune response that contributes to the development of myositis. However, the relationship between cancer and myositis is complex and is not yet fully understood.

Treatment of myositis usually involves both medications and physical therapy. It is very important to treat myositis as early and aggressively as possible to prevent severe muscle damage and ensure the best possible treatment outcome.

In rarer cases where myositis is accompanied by cancer, treating the cancer often helps the myositis. It is very important to treat the myositis as well as the cancer.

Prednisone

Prednisone is a corticosteroid commonly used as an initial treatment for myositis. It helps suppress the immune system and reduce inflammation that damages the muscles. Treatment often begins with a relatively high dose, which is gradually reduced over time as the condition improves and the treatment plan is adjusted.

Disease-Modifying Antirheumatic Drugs (DMARDs)

Disease-modifying antirheumatic drugs (DMARDs), which are also used to treat other autoimmune and rheumatic conditions, can help manage myositis. Common options include methotrexate and azathioprine (Imuran). These medications may be used alongside prednisone to improve disease control and help reduce the need for long-term corticosteroid treatment.

DMARDs can take several weeks to a few months to produce noticeable improvements. The choice of medication depends on the patient’s condition, response to treatment, and potential side effects.

Intravenous Immunoglobulin (IVIG)

Intravenous immunoglobulin (IVIG) is a treatment that involves administering antibodies through a vein. It may be recommended for certain patients with severe myositis or those who have not responded adequately to other treatments. IVIG can be particularly helpful in some cases, including when muscle weakness significantly affects swallowing or other essential functions. However, its effectiveness varies from person to person.

Physical Therapy and Exercise

Physical therapy and appropriately tailored exercise are important components of myositis treatment. They can help improve muscle strength, flexibility, mobility, and range of motion while reducing the effects of deconditioning. Regular physical activity, when suitable for the individual’s condition, may also help manage fatigue and improve emotional well-being.

A physiotherapist experienced in treating inflammatory muscle diseases can develop an individualized exercise program based on the patient’s strength, symptoms, and stage of recovery. Gentle stretching and gradual strengthening exercises may be beneficial, but the intensity and frequency should be adjusted to avoid overexertion. Early involvement in rehabilitation can help support recovery and maintain physical function.

Cancer Screening

Certain types of myositis, particularly dermatomyositis, are associated with an increased risk of cancer. For this reason, appropriate cancer screening is an important part of managing the condition. The recommended investigations depend on factors such as the patient’s age, type of myositis, symptoms, and individual risk profile.

In some cases, cancer may trigger an immune response that contributes to the development of myositis. When the two conditions occur together, treating the underlying cancer may also improve the muscle disease, although this outcome is not guaranteed.

Patients should inform their doctor if they have a first-degree relative, such as a parent, sibling, or child, who has had cancer. This family history may help guide decisions about appropriate screening and further investigations.

Dermatomyositis and polymyositis are two rare, chronic inflammatory diseases that affect the muscles. Both conditions cause muscle inflammation and weakness, but pain and swelling are not usually prominent symptoms. The main difference between the two is that dermatomyositis causes a characteristic skin rash, while polymyositis does not.

In severe cases, both conditions can affect the muscles involved in swallowing, making it difficult to swallow safely. This can lead to choking or aspiration, which occurs when food or liquid enters the airways or lungs. In rare cases, the diseases may also affect the heart muscle and the muscles responsible for breathing, potentially causing serious complications.

Dermatomyositis and polymyositis belong to a group of conditions known as inflammatory myopathies, which are diseases characterized by inflammation of the muscles.

Although these conditions can affect people of any age, they are more common in certain age groups. Dermatomyositis can occur in children, particularly those aged 10 to 15, while inflammatory myopathies in adults often develop between the ages of 45 and 60. Myositis is rare, affecting approximately 10 people per million, and women are about twice as likely as men to develop the condition.

There is currently no proven treatment that removes the existing CPP crystals, but symptoms can often be controlled effectively.

The choice of medication depends on kidney function, stomach health, heart conditions, other medications, and the severity of symptoms.

There is no specific diet proven to stopCalcium Pyrophosphate Deposition Disorder . A Mediterranean-style pattern—vegetables and fruit, whole grains, legumes, nuts, fish, and unsaturated fats—is a reasonable approach for overall health. Foods such as tomatoes and bell peppers can be included, but they shouldn’t be considered treatments for AS.

Tomatoes and arthritis

Tomatoes can be a nutritious addition to an arthritis-friendly diet, although they do not cure arthritis or directly reverse joint damage.

• Lycopene: Tomatoes are particularly rich in lycopene, an antioxidant that helps protect cells from oxidative stress. Cooked tomatoes and tomato products can provide especially well-absorbed lycopene.

• Vitamin C: Supports collagen formation and normal connective-tissue function.

• Antioxidants: Tomatoes contain vitamin C, carotenoids, and other plant compounds that contribute to overall antioxidant intake.

• Potential anti-inflammatory effects: Laboratory and observational research suggests that compounds in tomatoes may influence inflammatory pathways, but evidence that eating tomatoes significantly reduces arthritis pain or inflammation in people is still limited.

• Heart health: Tomatoes can contribute to a heart-healthy diet, which is particularly relevant for people with rheumatoid arthritis, because RA is associated with increased cardiovascular risk.

Some people with arthritis report that tomatoes or other nightshade vegetables worsen their symptoms. There isn’t strong scientific evidence that tomatoes generally cause arthritis inflammation or should routinely be avoided. If you consistently notice symptoms after eating a particular food, discussing this pattern with a healthcare professional or dietitian can be more useful than eliminating foods unnecessarily.

For osteoarthritis, tomatoes are best viewed as part of an overall nutritious eating pattern. For rheumatoid arthritis, diet can complement medical treatment but shouldn’t replace disease-modifying medication when it is prescribed.