Pyomyositis: Causes, Symptoms, and Management

Introduction:

Pyomyositis is a bacterial infection of skeletal muscles (muscles attached to the bones providing movement to the human body). The most common organism causing disease is Staphylococcus aureus. Sciba described the term pyomyositis in 1885. Levin reported the first case in 1971. Pyomyositis is also called tropical myositis. It usually results in single or multiple abscess formation through hematogenous spread (through the bloodstream and lymphatics). The most common sites are the thighs, shoulder, upper arm, and neck muscles. The distribution of pyomyositis is worldwide but more common in tropical and temperate areas, including Asia, Africa, North America, the United States, and the Caribbean. The disease is more common in temperate countries than in tropical countries.

What Are the Causes of Pyomyositis?

• The bacterium Staphylococcus aureus causes 90 % of the cases. One to five percent of cases are caused by group A Streptococcus. Other bacteria include group B, group C Streptococcus, Pneumococcus, and gram-negative bacilli. The bacteria cause problems when they enter the body.

• Trauma to the muscle, heavy exercise, and underlying health conditions are associated with disease development.

Who Does Pyomyositis Affect?

Pyomyositis affects all ages and races. The disease occurs in two age groups children aged two to five years and adults aged 20 to 45. The majority of the cases occur in adults. Males at birth are more commonly affected than females at birth. Most pyomyositis patients are healthy without any symptoms. Most of the patients in temperate areas are immunocompromised with several serious conditions.

1. Predisposing Factors:

• Trauma.

• Injection drug use.

2. Immunodeficiency: Immunodeficiency is a common factor in developing pyomyositis in temperate and tropical areas. Immunodeficiency disease includes.

• HIV (Human immunodeficiency virus is a virus that attacks the immune system of the human body).

• Diabetes mellitus (when the body does not use insulin and the pancreas does not produce enough insulin).

• Malignancy (presence of cancer).

• Organ transplantation.

• Malnutrition (nutritional deficiency).

3. Parasitic infections such as giardiasis, amoebiasis, and malaria.

4. Liver cirrhosis (a liver disease in which healthy liver tissue is replaced by fibrous tissue).

5. Renal insufficiency (poor function of kidneys).

How Does Pyomyositis Occur?

The mode of transmission of pyomyositis is hematogenous spread. The mode of transmission includes.

• Pyomyositis arises from the spread of infection through the bloodstream. The chemical removal of iron by myoglobin (a protein that carries and stores nutrients to the muscle cells) is an essential nutrient of growing bacteria.

• If Staphylococcus aureus is injected into the muscle, it fails to form an abscess. Trauma to a muscle can form abscesses because the bacteria get iron after trauma, which results in the growth of bacteria.

• Abnormality in the immune system may cause the disease. In HIV infection, the bacteria weakens the host defense, including the dysfunction of T-helper cells and granulocytes.

• HIV infection increases the incidence of staph carriers (infected with bacteria but without symptoms) compared to those not infected with HIV. If Staphylococcus aureus intravenous injection is given, then the abscess will develop in the damaged muscle and not in the healthy muscle.

What Are the Risk Factors of Pyomyositis?

The risk factors of pyomyositis include:

• People who are living in temperate areas.

• People who are suffering from HIV infection.

• Being immunocompromised.

• Diabetes Mellitus can damage the muscles and weaken the immune system.

• Heavy exercise and muscle trauma.

• During skin infection, the bacteria can travel deep inside the body to muscles.

• Intravenous drug injection.

What Are the Signs and Symptoms of Pyomyositis?

Pyomyositis can present with single or multiple abscesses. The most common sites involved are the muscles of the thighs, hips, shoulder, neck, and upper arm. The affected muscles are the abdominal muscle, spinal muscle, gluteal muscle, quadriceps, pectoralis major, and biceps.

Pyomyositis symptoms may occur in three stages. It includes.

1. Invasive Stage: The stage can last up to 10 to 21 days. The symptoms include widespread pain, fever, hematoma (blood clot in an organ or tissue), osteomyelitis (an infection of the bone), fascitis (inflammation of the fascia of the muscle), and thrombophlebitis (a blood clot that blocks veins in the legs).

2. Suppurative Stage: An abscess is formed in the muscle. The patient cannot walk properly if the affected muscle is on the leg. A hard mass develops in the muscle of the human body. Symptoms include high fever, nausea, vomiting, painful tenderness, and hard mass.

3. Late Stage: The third stage develops if the abscess remains untreated. The stage may cause complications. The abscess may extend to the bone and joint and cause septicemia (bacteria invade the bloodstream), septic shock, kidney failure, organ damage, and liver failure. The symptoms include organ failure with pain and fever and even may cause death. The stage is serious and life-threatening.

How Is Pyomyositis Diagnosed?

The disease is difficult to diagnose until the abscess gets large enough to be a noticeable lump under the skin. The diagnostic tests include.

1. Laboratory Tests - Thesefindings include leukocytosis (an increase in the number of white blood cells) and an increase in erythrocyte sedimentation rate (shows inflammation in the body).

2. Blood Culture - The test for the bacterium Staphylococcus aureus is positive.

3. Muscle Enzymes - These include increased creatine, phosphokinase, aldolase, aminotransferase, and lactic dehydrogenase levels.

4. Ultrasound Scan - It includes the hypoechoic areas (the areas that are darker than normal) with increased muscle bulk and collection of fluid.

5. Computed Tomography (CT) Scan - The scan is used to differentiate the tumor from the abscess. It shows a slight decrease or little loss of muscle planes and surrounding rim with contrast enhancement.

6. Magnetic Resonance Imaging (MRI) Test - The test shows a hyperintense rim (lesion in the brain that shows the area of high brightness) on weighted images. It shows detailed images of the inside of the body without using X-rays.

7. Biopsy - In this test, the pus is aspirated from the abscess and viewed under the microscope to see the staphylococcus aureus bacteria.

8. Physical Examination - The doctor may perform a physical examination to check the affected area for pain, mobility, and abscess formation.

How Is Pyomyositis Managed?

The treatment is given to prevent the disease. The treatment includes.

• Surgical drainage of the abscess.

• Prednisolone 1mg/kg/day is prescribed.

• Antibiotics are given, which include Penicillin, Flucloxacillin, and Vancomycin.

• Broad-spectrum antibiotics are given to patients with HIV infection and immunodeficiency patients.

• The doctor should continue the treatment even after the infection is clear from the body.

Conclusion:

Pyomyositis is known for its challenging and non-specific clinical presentation among patients in tropical, temperate areas. Although pyomyositis is not common, it is considered in patients with high fever and muscle pain. The disease must be diagnosed and treated early to decrease mortality (death rate). Awareness of the disease, early diagnosis, and prompt treatment will limit bacterial invasion and help eliminate and prevent disease.