What is the Cause of IIM?

Understanding the Root Causes of IIM

Idiopathic Inflammatory Myopathy (IIM) is a group of rare diseases that cause muscle inflammation and weakness, especially in muscles used for movement. It usually affects adults aged 40–60 and children aged 5–15.

Daily tasks like lifting or climbing stairs can become a real challenge in these conditions. Dermatomyositis is one type of IIM that may also cause a skin rash, while inclusion body myositis often affects grip and walking. Therefore, it is crucial to understand the causes and symptoms of this condition for early diagnosis and timely treatment.

Keep reading for a detailed insight.

What Causes Idiopathic Inflammatory Myopathy (IIM)?

The exact cause of IIM is not entirely known, but experts believe it results from a combination of genes and outside triggers. Here's a simple breakdown of what might lead to this condition:

• IIM is known as "idiopathic" because the exact reason it starts is still unknown.
• Genetic factors play an essential role, especially changes in genes that control the immune system.
• The HLA (Human Leukocyte Antigen) genes help the body recognise harmful invaders, but certain variations may confuse the immune system and cause it to attack healthy muscles.
• Environmental triggers—such as infections, some medications, or too much sunlight—may trigger the disease in people who are already at risk.
• Researchers are still exploring other possible causes, but many risk factors remain unknown.

What are the Common Symptoms of IIM?

IIM not only targets the muscles; it can even impact multiple body areas. Symptoms vary widely from person to person, and some signs may even look like other health conditions. Here’s a quick look at the most common symptoms:

• Muscle weakness is a major sign, mostly affecting the shoulders, arms, hips, and legs. It is hard to walk, climb stairs, or lift things.
• In many cases, the muscles used for swallowing are also affected, causing difficulty swallowing (dysphagia).
• Blood tests often show high levels of creatine kinase, an enzyme that increases with muscle damage.
• A special type called inclusion body myositis mainly causes weakness in the finger muscles and thigh (quadriceps) muscles.
• About half the patients experience skin changes. These mainly include a purple rash on the eyelids (heliotrope rash) or raised bumps over joints (Gottron’s papules), mostly in dermatomyositis. Skin symptoms may even resemble lupus or psoriasis.
• Some people develop thick, cracked skin on their hands and feet, known as "mechanic’s hands" or "hiker’s feet", which are also common in antisynthetase syndrome.
• Joint pain and swelling affect about 30% of patients, especially in the small joints of the hands and feet. Though it appears like rheumatoid arthritis, it usually does not damage the joints.
• Lung problems, such as shortness of breath or persistent cough, affect around 30% of people. They are more common in conditions like antisynthetase syndrome, dermatomyositis, and scleromyositis.
• Raynaud’s phenomenon, where fingers or toes change colour in cold or stress, also affects about 30%. It may cause small ulcers on fingertips and can be checked using a test called capillaroscopy.
• Heart issues, like chest pain, trouble breathing, or even stroke, affect around 9% of patients.

What is the diagnosis of IIM?

Diagnosing IIM mainly involves a few important tests and expert evaluation. Here are the primary diagnostic approaches doctors usually follow while treating IIM:

• If a patient shows common symptoms of IIM, special tests should be done in a centre experienced with these muscle diseases.
• Blood tests for autoantibodies are a major tool. Since IIMs are autoimmune diseases, many patients have specific autoantibodies that help confirm the diagnosis.
• Commercial testing kits now identify around 20 types of autoantibodies and can also help determine the kind of IIM.
• A muscle biopsy is still important. It generally involves taking a small piece of muscle to examine under a microscope.
• Even with advances in blood tests, a biopsy remains essential for confirming the diagnosis and ruling out other conditions.

What are the treatments for IIM?

Starting treatment early and working closely with IIM experts can help manage symptoms and improve daily life. Treatment's main goals are to control inflammation, protect muscles and organs, restore strength, and prevent long-term damage.

Here's a quick overview of how treatment is usually approached:

1. Induction Phase to Control the Disease Early : High-dose corticosteroids are used first to bring the disease under control. These steroids are slowly reduced over time to avoid long-term side effects.
2. Maintenance Phase to Keep Symptoms in Check : As steroids are lowered, immunosuppressant drugs are added to keep the disease in remission. The drug choice generally depends on the IIM type and which organs are involved. Moreover, other steps like sun protection, quitting smoking, and regular follow-ups also help prevent flare-ups.
3. Preventing and Reversing Long-Term Damage : Long-term damage, such as muscle loss, calcium deposits (calcinosis), or skin changes, may not improve with medication alone. Exercise therapy helps rebuild muscle strength. However, in some cases, surgery may be required to remove calcium buildup.
4. Cancer Screening and Treatment : About 10% of IIM patients may have an associated cancer. Treating the cancer usually improves the myopathy as well. Regular cancer checks are important, especially during the first 3 years after diagnosis.
5. Restoring Daily Function : IIM can impact a person’s ability to move and carry out everyday tasks. Therefore, physical and occupational therapy should begin early to improve mobility and quality of life.
6. Preventing Other Health Problems : IIM and its treatment can even increase the risk of infections, bone loss (osteoporosis), and heart issues. This can be reduced with vaccines, exercise, healthy food, and sometimes preventive medications.
7. Emotional and Social Support : Living with IIM can be difficult, so education and support groups are helpful. Connecting with others and learning more about the condition can make it easier to cope.

Controlling IIMs often requires long-term treatment, sometimes for years. While healthcare has improved over time, early diagnosis and better treatment are still needed to enhance quality of life.