viral myositis



OVERVIEW

Definition.

Viral myositis is a disease characterized by skeletal muscle damage following upper respiratory or gastrointestinal tract infections, which can present with temporary activity limitation, mainly in the form of muscle pain and lower limb weakness [1].

Viral myositis, also called epidemic myalgia, is a common complication of influenza in children and an infectious myositis, which is an inflammatory myopathy [2].

Morbidity

Viral myositis is most common in children and adolescents, and rare in adults, and is associated with epidemics of respiratory disease, often complicating influenza, with a higher incidence of the disease in winter and spring [2].

Etiology

Causes

Viral myositis has a complex etiology, with viral muscle infections being the main cause [3].

Among them, enteroviruses (e.g., coxsackievirus, echovirus, rotavirus, etc.), influenza virus and parainfluenza virus, herpes simplex virus, EBV, cytomegalovirus, HIV virus, and minuscule virus B19, etc., may cause viral myositis [4-5].

Predisposing factors

The following factors can trigger the above mentioned etiologic factors and cause flare-ups or exacerbation of the disease.

Lack of good hygiene habits, such as not washing hands regularly, poor indoor environment, and lack of ventilation.

Frequent use of public places without wearing masks for protection.

Lack of exercise, poor nutrition, etc. causing low immunity or resistance.

Symptoms

Main Symptoms

The main symptoms of viral myositis are skeletal muscle damage (e.g. muscle pain, muscle weakness), upper respiratory tract infection (e.g. fever, headache, cough), and digestive tract infection (e.g. abdominal pain, diarrhea).

Skeletal muscle injury

Usually 24-48h after the appearance of upper respiratory tract or digestive tract infection symptoms, sudden unilateral or bilateral lower limb pain, gait abnormality (e.g. walking on tiptoes) and bilateral lower limb weakness.

Usually, the gastrocnemius and flounder muscles are most frequently involved, followed by the proximal muscles of the lower limbs, while the muscles of the neck, shoulder, and upper limbs are occasionally involved, and physical examination is often accompanied by gastrocnemius grip pain [6].

Symptoms of upper respiratory tract infection

Symptoms of upper respiratory tract infection may appear in the early stage of the disease, mainly manifested as fever, headache, runny nose, cough, sore throat, etc. [2].

Digestive tract infection

Some patients may also have symptoms of gastrointestinal infection at the beginning of the disease, mainly manifesting as nausea, vomiting, abdominal pain, diarrhea and so on.

Complications

Rhabdomyolysis

When viral infection causes rhabdomyolysis, creatine kinase, lactate dehydrogenase, myoglobin and other related myocyte contents are released in large quantities and enter into the blood circulation, resulting in disturbance of the internal environment and impairment of organ function.

The main manifestations are muscle pain, oliguria, pressure pain, generalized weakness and so on [7].

Acute kidney injury

If the condition of rhabdomyolysis progresses, acute kidney injury can be induced due to renal ischemia, tubular occlusion and tubular oxide damage [8-9].

The main manifestations are decreased urine output, fatigue, anorexia, nausea and vomiting.

Consultation

Department of Medicine

Pediatrics

When children with fever, sore throat or abdominal pain, diarrhea and other symptoms are followed by muscle pain, muscle weakness, gait abnormalities and other manifestations, it is recommended to consult the pediatrics department in a timely manner.

Neurology

When limb weakness and gait abnormality appear, it is recommended to consult the Department of Neurology in time.

Emergency Medicine

If you experience severe headache, severe abdominal pain and diarrhea, or unbearable muscle pain, we recommend that you consult the Emergency Department.

Preparation for medical treatment

Preparation for medical treatment: registration, preparation of documents, and common problems.

Tips for the Emergency Department

It is recommended to wear loose clothing to the clinic to facilitate a full body physical examination.

Record the changes and characteristics of your condition to give your doctor more reference.

Preparation Checklist

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

Is there any muscle pain, muscle weakness, gait abnormality, etc.?

Is there fever, headache, cough, runny nose, sore throat, etc.?

Any nausea, vomiting, abdominal pain, diarrhea, etc.?

Any recent history of viral infections such as enterovirus, influenza virus, shingles, etc.?

Do you have AIDS?

Is there a history of upper respiratory system infection or gastrointestinal tract infection at the beginning of the disease?

Test results in the last six months, which can be brought to the doctor’s office

Laboratory tests: routine blood test, routine urine test, routine stool test, blood biochemistry (liver function, kidney function), cardiac enzyme profile, HIV antibody, pathogenicity test, etc.

Imaging examination: CT examination, magnetic resonance examination.

Other tests: electromyography and muscle biopsy.

Medication used in the last 3 months, if available, bring the box or package to the doctor’s office

Antiviral drugs: acyclovir, famciclovir, etc.

Sedative pain medications: aspirin, acetaminophen, etc.

Glucocorticoids: prednisone, methylprednisolone, etc.

Diagnosis

Diagnosis

Viral myositis can be diagnosed on the basis of patient history, clinical manifestations, laboratory tests, and imaging.

Medical history

The following is not necessary for the diagnosis of the disease, but if the following history is available, it may provide some reference for the diagnosis of the disease.

Recent history of viral infections such as enterovirus, influenza virus, and herpes zoster.

AIDS.

History of upper respiratory infections and gastrointestinal infections at the onset of the disease.

Clinical manifestations

Presence of skeletal muscle injury (e.g., muscle pain, muscle weakness), upper respiratory tract infection (e.g., fever, headache, cough), gastrointestinal tract infection (e.g., abdominal pain, diarrhea), and other manifestations.

Laboratory examination

The main focus is to find out whether the patient has experienced any hematologic abnormalities.

When the white blood cells are normal or decreased and the lymphocytes are increased, it usually indicates the presence of viral infection and helps to understand the cause of the disease.

It is important to know whether the patient has myoglobinuria.

The presence of myoglobin in the urine routine is diagnostic for the diagnosis of complications.

To find out whether the patient has developed a gastrointestinal infection.

When leukocytes appear in the stool routine, it is of guiding significance for the diagnosis of digestive tract infection.

Mainly include liver function, kidney function, etc.

Liver function tests of alanine aminotransferase and aspartate aminotransferase can understand the level of liver function, which has some significance in guiding the use of drugs.

Renal function tests mainly include blood creatinine, urea nitrogen and so on, when it appears different degrees of elevation, usually suggests the emergence of renal function damage, helps to understand whether the patient has complications.

It mainly includes creatine kinase, creatine kinase isoenzyme, lactate dehydrogenase, myoglobin and so on.

It is important to know if the patient has muscle damage.

When the cardiac enzymology indexes are abnormally high, especially creatine kinase, it is important for the diagnosis of the disease, in addition, myoglobin is also valuable for the diagnosis of rhabdomyolysis.

The main thing to know is whether the patient has AIDS.

When HIV antibody is positive, it usually indicates that the patient is infected with HIV, which is valuable in determining the cause of the disease.

It is important to know if the patient has any viral infections.

Including enteroviruses (such as coxsackievirus, echovirus, rotavirus, etc.), influenza virus and parainfluenza virus, herpes simplex virus, EBV, cytomegalovirus, microvirus B19 and so on.

If the test result is positive or the virus is detected, it is instructive for the diagnosis of the disease.

Imaging

CT examination can be used to find out whether the patient has respiratory infections, etc.

If the lung CT examination test is abnormal, it will help in the diagnosis of respiratory system infections and has some value in the diagnosis of the disease.

Magnetic resonance examination can be used to find out whether the patient’s muscles have lesions and the location of the lesions.

Skeletal muscle magnetic resonance imaging, as a noninvasive examination method, has good soft tissue contrast, which helps to understand muscle involvement and determine the nature of the disease [10].

Other examinations

Mainly include electromyography and muscle biopsy.

If EMG is positive, it has some significance in the diagnosis of the disease [11].

If the virus particles isolated in the muscle biopsy, it is of great significance for definite diagnosis. However, because it is an invasive test and also limited by the diagnostic level of the pathology department, it has not been widely carried out.

Differential diagnosis

Viral myositis generally needs to be differentiated from diseases such as dermatomyositis and polymyositis.

Dermatomyositis

Similarities: Both may present with muscle pain and muscle weakness.

Differences: Dermatomyositis is an inflammatory connective tissue disease mainly involving the skin and muscles, which not only presents with muscle pain and muscle weakness, but also skin damage, such as periorbital purplish-red spots, exposure site rash, and perinail erythema, etc., whereas viral myositis usually does not have the above mentioned manifestations of skin damage [12].

Polymyositis

Similarities: Both may present with muscle pain and muscle weakness.

Differences: Polymyositis usually manifests as progressive weakness of limbs or both upper limbs, which is obvious in the proximal part, and manifests as difficulty in lifting arms and objects, and only some patients have muscle pain; while viral myositis usually manifests as weakness of lower limbs, and mainly manifests as muscle pain.

Treatment

Aim of treatment: to remove the cause of the disease, relieve the symptoms and prevent complications.

Treatment principle: early diagnosis, early treatment. General treatment and drug treatment are usually adopted.

General treatment

Strengthen nutrition, ensure the intake of calories and water.

Avoid cold and take good protection.

If the muscle pain is obvious, it can be appropriate to limit the activities and bed rest.

Medication

Antiviral drugs

Commonly used drugs include acyclovir and famciclovir.

They are suitable for patients who develop viral infection.

It is contraindicated for those who are allergic to this product. Common adverse reactions are nausea, vomiting, diarrhea, loss of appetite, thirst, etc.; joint pain, headache, dizziness and other manifestations may occur with prolonged oral administration.

Antipyretic and analgesic drugs

Commonly used drugs include aspirin and acetaminophen.

It is suitable for patients with fever and muscle pain.

Common adverse reactions to aspirin are gastrointestinal reactions, such as nausea, vomiting, epigastric discomfort, etc. It is contraindicated for those who are allergic to the product, pregnant women, lactating women, active ulcer disease, thrombocytopenia, hemophilia. Acetaminophen can cause nausea, vomiting, sweating, abdominal pain, skin pallor and other adverse reactions, severe hepatic and renal insufficiency patients and those who are allergic to the product are prohibited.

Glucocorticoid

Commonly used drugs are prednisone, methylprednisolone and so on.

It is suitable for patients with very severe pain, usually choose short-term application of glucocorticosteroids, and can be reduced and stopped when symptoms improve [13].

Long-term application of glucocorticosteroids may lead to side effects such as infection, osteoporosis, drug-induced diabetes mellitus, and aseptic necrosis of the femoral head in a small number of cases, which needs to be monitored and handled in a timely manner.

Prognosis

Cure

If timely and regular treatment, viral myositis can basically be cured, usually about 1 week to relieve the symptoms, myalgia disappears, the prognosis is good [13].

Prognostic factors

The prognosis of viral myositis is affected by many factors, and the following factors may lead to a poor prognosis.

Irregular work and rest, overexertion, and inadequate sleep.

Failure to rest in bed during the acute attack, and continuing to engage in activities.

Not paying attention to diet and consuming too much spicy and stimulating food.

Poor physical condition, recurrent respiratory infections, digestive tract infections, etc.

Disease diagnosis or treatment is not timely enough, leading to aggravation of the condition and serious complications.

Daily

Daily Management

Dietary management

Avoid intake of spicy and stimulating foods, frying and deep-frying, etc. Avoid intake of coffee, strong tea and other drinks that affect sleep.

Ensure balanced nutrition, adequate intake of calories and water, and supplement foods that are high in protein (e.g., milk, eggs, lean meat), vitamins (e.g., fresh vegetables and fruits), and easy to digest.

Life Management

Ensure sufficient rest and sleep, keep the indoor environment comfortable, with good air circulation, and open the windows regularly every day for ventilation.

Wear a mask when going out to avoid recurrence of infection.

After the symptoms are relieved, you can do activities and exercise appropriately.

Psychological support

Family members are advised to help patients build up confidence and encourage them to eliminate negative emotions in an appropriate way, so that they will be emotionally stable and comfortable, and actively cooperate with the treatment.

Disease monitoring

Observe the color of urine, whether there is any deepening of urine color or hematuria.

Monitor the urine volume in 24 hours, if the urine volume decreases significantly, inform the doctor for symptomatic treatment.

Follow-up review

Adjust the drug dosage according to the results of the follow-up examination. Regular follow-up can keep abreast of the changes in the condition and provide early symptomatic treatment, which can delay the progression of the disease and prevent the occurrence of complications.

Regular checkups should be conducted according to the doctor’s instructions, and the cycle of checkups usually lasts for 1 to 2 weeks.

The follow-up may require routine blood tests, urine tests, routine stool tests, blood biochemistry, cardiac enzymology, pathogenetic tests and other related tests.

Prevention

The causes of viral myositis are complex and difficult to prevent effectively, but the risk of developing the disease can be reduced by, for example, the following healthy lifestyles or behaviors.

Take rest, avoid staying up late and over-exertion.

Exercise properly and eat a balanced diet.

Maintain good living habits, wash your hands frequently, practice good hand hygiene, keep the room clean and tidy, and ventilate frequently.

Avoid gathering of people, wear a good mask in public places, and do a good job of protection.

It is recommended to actively carry out influenza vaccination [14].