OVERVIEW

What is Polymyositis?

Polymyositis is an autoimmune disease and one of the common types of idiopathic inflammatory myopathies. The exact cause remains unclear, and its clinical manifestations primarily include progressive weakness and muscle pain in the symmetrical proximal limbs, neck, and pharyngeal muscles.

Are Polymyositis and Dermatomyositis the Same?

Both polymyositis and dermatomyositis involve inflammatory changes that lead to skeletal muscle degeneration, necrosis, atrophy, and regeneration. However, they are not the same condition. The specific differences are as follows^[1]:

1. Affected Areas: Polymyositis only involves skeletal muscles, while dermatomyositis affects both skeletal muscles and the skin.
2. Causes: The underlying causes differ. Polymyositis is an autoimmune disorder with an unclear etiology, generally believed to be triggered by immune factors. Dermatomyositis is an inflammatory condition occurring in striated muscles, primarily caused by lymphocyte infiltration. It is often associated with genetic predisposition and viral infections.
3. Symptoms: In addition to muscle weakness, dermatomyositis patients also exhibit skin lesions. Rashes may appear around the eyes and eyelids as edematous, purplish patches. Facial involvement can include butterfly-shaped erythema and other skin damage.

SYMPTOMS

What are the common manifestations of polymyositis?

The common clinical manifestations of polymyositis are as follows:

1. Progressive symmetric proximal muscle weakness. Early symptoms may include difficulty squatting, running, jumping, or climbing stairs. As the disease progresses, patients may also experience difficulty raising their head or lifting their arms.
2. Fatigue. Patients often feel general weakness throughout their body.
3. Weight loss. As the condition worsens, patients may notice significant weight loss.
4. Fever. Patients may develop low-grade or moderate-to-high fever, along with pale lips.
5. Dysphagia and spasmodic cough. When swallowing muscles are affected, patients may struggle to swallow food and experience throat discomfort after eating or drinking, leading to spasmodic coughing (also known as choking cough).
6. Dyspnea. If respiratory muscles are involved, patients may feel difficulty breathing or shortness of breath. In severe cases, their face and lips may turn bluish-purple.
7. Joint swelling and pain. Patients may experience swelling, pain, and restricted movement in joints such as the limbs and knees.
8. Muscle atrophy. Patients may notice their muscles gradually thinning and weakening.

What are the possible accompanying symptoms of polymyositis?

Accompanying symptoms of polymyositis include manifestations of the digestive system, such as nausea, bloating, and vomiting; cardiovascular symptoms, such as chest tightness and shortness of breath; renal symptoms, such as hematuria and proteinuria; and in rare cases, autoimmune system involvement leading to rheumatoid arthritis-like symptoms, such as proximal joint pain and swelling.

1. Digestive system. If the digestive system is affected, symptoms such as bloating, nausea, vomiting, and abdominal pain may occur.
2. Cardiovascular system. If the cardiovascular system is involved, patients may experience chest tightness, shortness of breath, and in some cases, arrhythmia.
3. Renal system. After the onset of the disease, patients may develop symptoms such as hematuria and proteinuria.
4. Autoimmune system. Some patients may develop rheumatoid arthritis, presenting with morning stiffness, swelling, and pain in proximal joints.

CAUSES

What are the common causes of polymyositis?

The exact cause of polymyositis remains unclear, but it is often associated with genetic factors, viral infections, and immune system dysfunction^[3].

1. Genetic factors. There have been reports of polymyositis occurring in families, suggesting a possible genetic link.
2. Viral infections. Some patients have a history of infections with viruses such as influenza, HIV, or Coxsackie virus before the onset of the disease.
3. Immune system disorders. Conditions like rheumatoid arthritis, systemic lupus erythematosus, and Sjögren's syndrome may be related to polymyositis.
4. Possible association with malignancies. Patients diagnosed with polymyositis, especially those over 40, should undergo thorough examinations to rule out underlying malignancies, such as lung cancer. If no tumor is initially detected, regular follow-ups are recommended.

What diseases are associated with polymyositis?

Polymyositis may be linked to autoimmune diseases such as systemic lupus erythematosus and Sjögren's syndrome.

The exact cause of polymyositis is unknown, but it may be related to autoimmune disorders, including systemic lupus erythematosus, Sjögren's syndrome, rheumatoid arthritis, and scleroderma.

Patients suspected of having polymyositis, particularly those over 40, should undergo comprehensive tests to identify potential causes, including malignancies like lung cancer. If no tumor is found initially, regular monitoring is advised.

Diagnostic tests for polymyositis may include erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), complete blood count (CBC), electromyography (EMG), and, if necessary, rheumatoid factor, tumor markers, immunological tests, or chest CT scans. Timely treatment is recommended after diagnosis.

Is polymyositis hereditary?

Polymyositis may have a genetic component^[3].

About half of polymyositis cases are associated with HLA-DR3, and HLA-DR52 is found in most patients, suggesting a genetic link. Additionally, familial cases of polymyositis have been reported, further supporting a hereditary connection.

If either parent has a history of polymyositis, caution is advised. Those planning pregnancy should consult a medical professional for genetic testing.

DIAGNOSIS

What tests are needed for suspected polymyositis?

For suspected polymyositis, the following tests are generally required:

• Muscle strength examination: Aims to assess the patient's muscle strength level and determine the severity of the condition^[1].
• Physical examination: The doctor will evaluate the nature and location of the lesions through cardiac and pulmonary physical examinations.
• Electromyography (EMG): Determines whether the patient has myogenic damage.
• Autoantibody testing: Helps doctors evaluate treatment efficacy and assist in diagnosis.
• Serum muscle enzyme profile: Aids in confirming the diagnosis of the disease.
• Muscle magnetic resonance imaging (MRI): Assesses the extent of muscle damage.
• Chest CT: Helps doctors determine whether there is lung damage and its severity.
• Cardiac ultrasound: Evaluates the patient's cardiac function.
• Muscle biopsy: Assists in confirming the diagnosis and assessing the condition^[2].

Which diseases are easily confused with polymyositis?

Diseases that may be confused with polymyositis include inclusion body myositis, limb-girdle muscular dystrophy, and myasthenia gravis.

1. Inclusion body myositis: This condition also presents with inflammatory muscle damage and should be differentiated from polymyositis. Symptoms include asymmetric muscle weakness, commonly affecting the quadriceps and distal muscle groups. Serum creatine kinase levels are usually normal, and muscle biopsy reveals eosinophilic inclusions.
2. Limb-girdle muscular dystrophy: This disease causes proximal limb muscle weakness, involving the pelvic and shoulder girdles. Creatine kinase levels may be elevated, but pathological examination shows no inflammatory cell infiltration.
3. Myasthenia gravis: Patients experience muscle weakness, with symptoms improving in the morning or at rest and worsening in the evening or with fatigue. Serum enzyme levels remain normal.

TREATMENT

Which department should I visit for polymyositis?

For polymyositis, it is recommended to consult the rheumatology and immunology department.

Can polymyositis be cured?

Polymyositis currently cannot be completely cured, but if patients receive timely and proper treatment, the condition can be effectively controlled in most cases.

The majority of children and young adults can achieve significant improvement with early and active treatment. In the early stages, patients may experience intermittent muscle pain and weakness. Prompt treatment with corticosteroids and other medications can effectively improve symptoms in most patients.

If patients have severe underlying conditions such as chronic obstructive pulmonary disease (COPD) or diabetes, the disease may recur. Additionally, the presence of lung tumors should be ruled out, as these conditions can affect the prognosis of polymyositis.

What is the prognosis for polymyositis?

With timely and proper treatment, most patients with polymyositis can achieve effective control of their condition. However, a small number of refractory cases may be difficult to manage and could even worsen. Without prompt treatment, the disease may progressively worsen, leading to impaired function of vital organs and potentially affecting quality of life and lifespan.

DIET & LIFESTYLE

What should patients with polymyositis pay attention to in daily life?

In daily life, patients with polymyositis should pay attention to the following aspects:

1. Monitor the condition and attend follow-up visits. Since polymyositis cannot be completely cured and may recur, patients should pay attention to whether their condition worsens or relapses and attend regular follow-up visits as required by the doctor.
2. In terms of diet, it is recommended to consume high-quality protein, with low fat and low salt. For patients with swallowing difficulties, liquid or semi-liquid foods can be chosen. Additionally, patients with polymyositis are advised to quit smoking and drinking.
3. In terms of exercise, bed rest is recommended during disease flare-ups to avoid aggravating symptoms. However, after symptoms alleviate, moderate exercise is advised to prevent muscle atrophy, gradually increasing the intensity and duration of workouts. Avoid strenuous exercise and excessive fatigue.
4. During medication, patients with polymyositis should avoid crowded places to prevent upper respiratory infections. Female patients should maintain genital hygiene to prevent urinary tract infections.

How can polymyositis patients monitor changes in their condition?

Methods for polymyositis patients to monitor changes in their condition include observing muscle pain and weakness, and regularly checking creatine kinase levels.

1. Observe for muscle pain. Polymyositis is characterized by muscle pain. If a patient with a history of polymyositis experiences calf pain recently, a recurrence should be ruled out. Physiological causes, such as excessive physical activity, should also be excluded.
2. Observe for muscle weakness. A typical feature of polymyositis is proximal limb muscle weakness. If muscle weakness occurs recently, it is recommended to visit a neurology department for further examination.
3. Regularly check creatine kinase levels. Patients should follow their doctor's instructions to regularly test creatine kinase levels. If abnormalities are found, diagnosis and treatment should be guided by a doctor.

If abnormalities are detected through self-monitoring, medical attention should be sought promptly to avoid worsening the condition.

How can family members of polymyositis patients provide proper care?

Care for polymyositis patients by family members includes attention to diet, exercise, and emotional support.

1. Diet. After the onset of polymyositis, a high-protein, high-vitamin diet should be provided. Patients should consume protein-rich foods such as lean meat, milk, eggs, and soy products to enhance immunity and supply essential nutrients. They should also eat plenty of vegetables and fruits, which are rich in vitamins and minerals, to boost metabolism and replenish hydration.
2. Exercise. During flare-ups, patients should rest appropriately and avoid excessive exercise to prevent worsening the condition.
3. Emotional support. After the onset of the disease, family members should communicate with the patient, encourage them to cope with the condition, and actively pursue treatment and rehabilitation to help overcome anxiety and depression.

PREVENTION

How to Prevent Polymyositis?

To prevent polymyositis, the following measures are recommended:

1. Boost immunity to resist viral infections. Certain viral infections may trigger an autoimmune response in patients, leading to polymyositis.
2. Use medications rationally. Individuals with chronic conditions such as hyperlipidemia or cardiovascular diseases should take medications under medical supervision.
3. For those with high-risk conditions like immune system disorders or malignant tumors, regular check-ups and follow-ups are advised.