polymyositis



OVERVIEW

Definition

Polymyositis is a diffuse inflammatory disease of skeletal muscle characterized by involvement of the proximal muscles of the extremities.

Epidemiology

The prevalence of the disease is 0.1 to 0.9 per 100,000 population.

It is most common in women aged 30 to 60 years.

It is rare in children.

Causes

Causes

The cause of the disease is not clear. Genetic, infectious, and immunologic factors may be involved in the development of the disease.

Families with polymyositis have been reported, suggesting that genetic factors are involved in the pathogenesis.

Influenza viruses A and B, human immunodeficiency virus, echovirus, and coxsackievirus infections may induce polymyositis.

Jo-1 antibodies, SRP antibodies, Mi-2 antibodies, or mitochondrial antibodies may be measured in the serum of some patients.

Pathogenesis

The pathogenesis of polymyositis is related to immune dysregulation, including abnormalities in cellular and humoral immunity.

T-lymphocyte-mediated myocyte immunotoxicity.

Specific cytotoxic antigens mediate the expression of MHC class I molecules by T-lymphocytes (CD8) that are damaging to their own muscle fibers.

Symptoms

Polymyositis often has a subacute onset, with muscle weakness (eye and facial muscles are almost unaffected) occurring within weeks to months, often accompanied by joint and muscle pain. Only a few patients may have an acute onset. In severe cases, swallowing, slurred speech and dyspnea may occur.

Typical symptoms

Symmetrical proximal muscle weakness of the limbs

Shoulder and neck muscle weakness is the first symptom.

When the proximal muscles of the upper limbs are involved, there may be difficulty in lifting the arms, combing the hair and dressing.

When the proximal muscles of the lower limbs are involved, it often manifests as difficulty in walking up and down stairs, squatting or standing up from a seat.

It gradually progresses to an inability to walk or stand.

Cervical flexor weakness

Difficulty in raising the head when lying down.

The head is often tilted back.

Pharyngeal muscle weakness

Slurred speech, choking, difficulty swallowing.

Joint and muscle pain

Muscle pain is present in 5% to 10% of patients.

The pain is not severe.

It is usually seen in the early stage of the disease.

Systemic symptoms

Pulmonary involvement

Respiratory muscle involvement may be characterized by shallow breathing, dyspnea, and cyanosis.

About 16% of patients combine with interstitial pneumonia and present with chest tightness, shortness of breath, and cough.

Symptoms of digestive tract involvement

Acid reflux, dysphagia, nausea, vomiting, abdominal pain, etc.

Symptoms of heart involvement

Palpitation, syncope, dyspnea, double lower limb edema and other symptoms.

Kidney Involvement Symptoms

Proteinuria may occur, manifested by eyelid edema.

Hematuria.

Consultation

Department of Medicine

Department of Rheumatology and Immunology

Prompt medical attention is recommended if symptoms such as weakness of the limbs, muscle pain, difficulty in lifting the head, with or without chest tightness, cough, difficulty in swallowing, etc. are present.

Emergency Department

If you experience generalized edema, dyspnea, fainting, etc., it is recommended that you consult the Emergency Department or call the 120 emergency number as soon as possible.

Preparation for medical treatment

Preparation for medical consultation: registration, preparation of documents, common problems

Tips for seeking medical treatment

For people with mobility problems, it is recommended that their family members accompany them to the clinic, and the patient can move around with the help of a wheelchair or crutches in order to prevent falls or accidents.

Avoid self-medication before seeking medical treatment, so as not to cover up the condition.

If you have many clinical symptoms, try to record the symptoms and characteristics of the attack, so as to give more reference to the doctor.

Preparation checklist for medical consultation

Particular attention should be paid to the time of symptom onset, special manifestations, etc.

When did the muscle weakness worsen and when did it abate?

Has there been coughing, weakness of breathing, or even a feeling of breathlessness?

Is there any joint or muscle pain?

Is it accompanied by slurred speech, choking on water, or difficulty swallowing?

Has anyone in the family had polymyositis?

Is there a history of systemic sclerosis, systemic lupus erythematosus, dry syndrome, or polyarteritis nodosa?

Test results from the last six months to bring to the doctor’s office

Laboratory tests: magnetic resonance imaging, routine urine test, serum myosin test, autoantibody test

Imaging tests: joint ultrasound, lung X-ray or CT, cardiac ultrasound

Others: electromyography, muscle biopsy

Medications used in the last 3 months, if available, bring the box or package with you to the doctor’s office.

Analgesics: indomethacin, acetaminophen, diclofenac, ibuprofen

Immunosuppressants: azathioprine, methotrexate

Others: Prednisone

Diagnosis

Disease Diagnosis

The diagnosis of polymyositis is based on the history, clinical manifestations, ancillary findings, and exclusion of other diseases.

History

Female aged 30 to 60 years.

Subacute onset of disease.

There may be a history of colds and other infections before the disease.

History of other connective tissue diseases such as systemic sclerosis, systemic lupus erythematosus, desiccation syndrome, polyarteritis nodosa.

A relative with polymyositis.

Clinical manifestations

Progressively worsening muscle weakness (eye and facial muscles are almost unaffected), often accompanied by joint and muscle pain. In severe cases, slurred speech and dyspnea may be present.

Laboratory Tests

Blood: mild anemia, increased white blood cell count.

Urine routine: increased 24-hour urinary creatine, some patients may have myoglobinuria.

Serum muscle enzymes: serum muscle enzymes (e.g. creatine kinase, lactate dehydrogenase, glutamate aminotransferase, etc.) are elevated during the active phase, of which the elevation of creatine kinase is the most sensitive.

Autoantibody test: commonly positive for myositis-specific antibodies, myositis-associated antibodies, antinuclear antibody profile, rheumatoid factor, etc.

Erythrocyte sedimentation rate: increased speed is often seen during the active phase of the disease.

C-reactive protein: often elevated during the active phase of the disease.

Renal function: creatinine and urea nitrogen may be elevated.

Imaging

Magnetic resonance imaging (MRI): diffuse or focal edema is seen on muscle MRI of the limbs (regular thighs and calves).

Lung X-ray or CT: examination may reveal flaky shadows in the lungs.

Cardiac ultrasound: pericardial effusion, cardiac valvular lesions.

Other tests

Electromyography

Muscle biopsy

Differential diagnosis

Lipid deposition myopathy

Similarity: Weakness of the proximal extremities and elevated creatine kinase.

Differences: Lipodystrophic myopathy has an adolescent onset, and muscle weakness is exacerbated by exercise and is accompanied by muscle swelling and pain. Muscle biopsy reveals lipodystrophic myopathy.

Myotonic dystrophy of limb band

Similarities: Weakness and atrophy of the proximal limbs and pelvic and scapular girdle, increased muscle enzymes.

Differences: Myotonic dystrophy of the limb-girdle type often has a family history, no myalgia, and the disease progresses more slowly. There is no significant inflammatory cell infiltration on muscle biopsy.

Myasthenia gravis

Similarity: weakness of the limbs.

Difference: Myasthenia gravis has the phenomenon of “light in the morning and heavy in the evening”, there is no muscle pain, and electromyography shows decreasing phenomenon of heavy frequency stimulation.

Treatment of myasthenia gravis

General treatment

The patient should have a correct understanding of the disease, maintain a good psychological state and build up optimism.

In the acute stage, bed rest is needed, and passive movement of limbs should be carried out, avoiding dragging, pulling, pushing and other movements.

During the remission period, you can choose the appropriate exercise mode according to your condition under the guidance of your doctor.

High-calorie, high-protein diet is recommended.

Pay attention to the changes of your condition, once the symptoms worsen or recur, you should go to the hospital in time.

Medication

During drug treatment, you should strictly follow the doctor’s instructions, do not change the dose of drugs without authorization or suddenly stop taking drugs, to ensure that the treatment plan is implemented. Do not believe in unrecognized treatments such as local remedies, secret remedies, and biased remedies.

Glucocorticoid

Glucocorticosteroids are the drugs of choice for the treatment of polymyositis.

Prednisone and methylprednisolone are available.

Acute or severe patients can be high-dose methylprednisolone shock treatment.

If the clinical symptoms are relieved and stabilized, the creatine kinase is basically normal, and the electromyogram has no spontaneous activity, the dose can be gradually reduced according to the doctor’s opinion until the drug is stopped.

Long-term application of glucocorticoids should pay attention to infection, osteoporosis, hypokalemia and other adverse reactions.

Immunosuppressant

Immunosuppressants can be added to glucocorticoid-insensitive, poorly tolerated patients and some patients with more severe disease onset.

Currently, the most commonly used immunosuppressive drugs are azathioprine and methotrexate.

The use of azathioprine requires close monitoring of the patient’s blood counts and liver function, especially in the first month of use, and it is recommended that the patient be reviewed regularly according to the doctor’s instructions.

Methotrexate carries a potential risk of lung damage and is generally not used in patients with concomitant interstitial pneumonia. Adverse reactions such as myelosuppression, hepatic damage and gastrointestinal symptoms should also be noted during administration.

Immunoglobulin

In the acute stage, it can be used in combination with other therapeutic drugs with better results.

Immunoglobulin can be administered intravenously.

Adverse effects include nausea, vomiting, and dizziness, but most resolve spontaneously.

Prognosis

Cure

Half of the patients with polymyositis will recover from the disease.

Some patients can be taken off medication and remain stable for a long period of time after regular treatment.

Some patients experience alternating relapses and remissions or have persistent activity and require long-term drug therapy.

Hazards

The symptoms such as weakness of limbs, muscle pain, difficulty in lifting the head, joint pain, etc. can seriously affect normal work and life.

If long-term use of glucocorticoids prone to infections, osteoporosis, hypokalemia, hypertension, hyperglycemia, hyperlipidemia and other serious adverse reactions, further affecting health and quality of life.

Those with esophageal, pharyngeal and respiratory muscle involvement or interstitial pulmonary fibrosis have a poor prognosis.

The most common causes of death are lung infection, pulmonary fibrosis, respiratory muscle paralysis, cardiac damage and malignancy.

Daily life

Daily life

Diet

It is advisable to choose a diet high in protein and vitamins and rich in potassium and calcium.

Avoid eating spicy and stimulating foods, such as wine, strong tea, coffee, raw garlic, ginger, chili peppers, curry and so on.

Dysphagia patients try to take a sitting position when eating, avoid eating dry, hard and rough food.

Give the patient enough time to eat, if you feel weak in chewing, you should take a proper rest before continuing to eat.

When choking on water, the patient should not be forced to take medicine and eat.

Serious patients can be given nasal fluid diet.

If there is a significant reduction in food intake, weight loss, mental instability, loss of skin elasticity and other signs of malnutrition, it should be promptly consulted.

Lifestyle

Bed rest should be given in the acute stage.

During the recovery period, appropriate activities can be carried out early in the morning, after rest or when the symptoms of muscle weakness are mild, and it is better not to feel fatigue.

When clinical symptoms are obvious, family members can assist the patient to carry out washing, eating, dressing and other life activities.

Avoid driving and cycling when there are obvious symptoms of limb weakness.

Pay attention to the cleanliness of the environment and open the windows regularly for ventilation.

Avoid going to places where people gather.

Observe weather changes and increase clothing appropriately in cold weather.

Strictly quit smoking and avoid exposure to “second-hand smoke”.

Adjustment of mindset

Face the disease with a positive and optimistic attitude and build up confidence in overcoming the disease.

Talk to your family, partner and friends about your inner feelings.

Those who have difficulty speaking can use communication tools such as paper, pens and drawing boards to express their needs to others in written form and body language.

Strive to take care of yourself or participate in jobs that you can do to enrich your life.

Prevention

If a relative has polymyositis, he or she should have regular medical checkups and seek prompt medical attention if he or she becomes unwell.

Actively treat autoimmune or other systemic diseases.

Eat a balanced diet with a variety of food types.