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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]

Synonyms and keywords: Tropical pyomyositis; Myositis tropicans; Bungpagga; Lambo lambo; Tropical skeletal muscle abscess; Myositis purulenta tropica; Bacterial myositis; Suppurative myositis; Epidemic abscess


Pyomyositis, also known as tropical pyomyositis or myositis tropicans is an acute primary deep bacterial infection of the skeletal muscles that results in a single or multiple pus-filled abscesses. This condition is more common in tropical areas but may also occur in the temperate zones. The majority of pyomyositis is caused by the bacterium Staphylococcus aureus. In tropical regions, the infection often follows minor trauma, while in temperate zones the infection typically occurs in people with immune deficiencies. The abscess within the muscle is drained surgically and antibiotics are administered to fully clear the infection. The infection can affect any skeletal muscle, but most commonly infects the large muscle groups such as the quadriceps or gluteal muscles.[1][2]

Historical Perspective

  • Traquair credited Virchow for the earliest mention of pyomyositis, however it was first described by Scriba in 1885 as a disease endemic to the tropics, hence the term tropical myositis.[3][4]
  • Levin et al. reported the first case from a temperate region in 1971.


  • Pyomyositis may be classified according to the International Classification of Diseases-10 (ICD-10) into:[5]
  • M60.0 Infectious myositis, Tropical pyomyositis (optionally, B95-B97 to indicate the infectious agent; B95.6 for Staphylococcus aureus)
  • Based on prognosis, pyomyositis is classified into three stages:



Common locations

Commonly involved muscles include:[6][2][7][8]

Microscopic histopathological analysis

On microscopic histopathological analysis, the following are characteristic findings of pyomyositis in sequence:[2]


Pyomyositis is an acute bacterial infection of skeletal muscle.[3][9]


Most common cause of pyomyositis includes:

Less common causes of pyomyositis include:

Rare causes of pyomyositis include:

Differentiating Pyomyositis from Other Diseases

  • It does not include:

Epidemiology and Demographics

Tropical countries

  • Majority (1,000-4,000 per 100,000 of all hospital asmissions) of pyomyositis cases are reported in some tropical countries such as Asia, tropical Africa, Oceania (islands of tropical pacific ocean), and the Caribbean islands.
  • Between 1980-1989, the incidence of pyomyositis was approximately 2,000 per 100,000 of surgical admissions in Ecuador. [11]

Temperate countries

  • In temperate countries, such as the United States, pyomyositis was a rare condition (accounting for 1 in 3000 pediatric admissions), but has become more common since the appearance of the USA300 strain of MRSA, especially in immunocompromised patients.[12][13]


  • In tropical countries, pyomyositis most commonly affects children and young adults but may occur in any age group.[3][14]
  • In temperate countries, the majority of pyomyositis cases occur in adults and elderly patients.


  • In tropical countries, males are more commonly affected than females.[3][14]
  • In temperate countries, both males and females are equally affected.

Risk Factors

The common risk factors in the development of pyomyositis include:[2][15][16][17][18]


According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for pyomyositis.

Natural History, Complications, and Prognosis

Natural History

If left untreated, pyomyositis is a potentially life threatening condition (mortality rate of 0.5-2%) which may progress to develop bacteremia, septicemia, metastatic abscess, acute renal failure, septic shock, and death.


Common complications of pyomyositis include:[19][2]

Cardiac complications

Other complications


  • Based on prognosis, pyomyositis is classified into three stages:
  • Depending on the clinical stage of pyomyositis at the time of diagnosis, the prognosis may vary. However, the prognosis is generally good when diagnosed and treated properly.[2]


Early diagnosis of pyomyositis is critical for good prognosis but is often missed due to following:[2]

  • Unfamiliarity with the disease
  • Atypical presentations
  • A wide range of differential diagnosis
  • Lack of early specific signs


A detailed and thorough history from the patient is necessary. Specific areas of focus when obtaining a history from the patient include:[20]


The symptoms of pyomyositis are divided into three stages[3][20]

Stage Clinical features
Invasive stage ● Lasts 1-2 weeks
● With or without fever
● Firm swelling
● Localised pain
● Loss of apetite (anorexia)
Purulent or
Suppurative stage
● Next 2 weeks
● High spiky fever
● Firm mass with pus
Late or
Septic stage
● Fluctuant mass
● Dissemination of infection
Acute renal failure
● Metastatic abscesses
Septic shock
● Death

Atypical symptoms

The atypical symptoms of pyomyositis include:[2][21]

Physical Examination

Common physical examination findings of pyomyositis include:[3][20]

Stage General appearance Vitals Local examination
Invasive stage Ill apprearing Low raise in temperature With or without tenderness
Indurated or woody hard
Localised raised of temperature
Suppurative stage
Severely ill High rise in temperature Marked tenderness of affected muscle
Fluctuant mass
Localised raised of temperature
Septic stage
Acutely ill
Altered mental status
High rise in temperature
Fluctuant swelling in muscle


Laboratory Findings

Laboratory findings consistent with pyomyositis include:[2]

  • Needle aspiration (gold standard for diagnosis)
  • Negative for pus in invasive stage
  • Positive for pus in suppurative and septic stage
  • Aspirated pus is sent for culture (aerobic and anaerobic culture)
  • Biopsy (gold standard for diagnosis)
  • Biopsy of the abscess wall and muscle taken at the time of abscess drainage should be cultured
  • Blood culture and sensitivity helps to identify the following:
  • Septicemic process in blood
  • Antibiotics of choice
  • Hematological tests:
  • Other laboratory tests to identify risk factors

Imaging Findings

The following non invasive imaging studies can be used in the diagnosis of pyomyositis:


  • Ultrasonography is the initial imaging study of choice.
  • On ultrasonography, pyomyositis is characterized by the following features:[22][23]
  • Muscle swelling
  • Heterogenous hypoechoic areas
  • Hypoechoic areas
  • Hyperechoic areas

CT scan

  • On CT scan, pyomyositis is characterized by the following features:
  • The affected muscle shows areas of low attenuation with loss of muscle planes
  • Surrounding rim of contrast enhancement


  • On MRI, pyomyositis is characterized by the following features:[24][25]
  • The affected muscle may appear swollen, with loss of architectural definition
  • Heterogenous areas of low intensity appear on T1-weighted images
  • In the early stage, the only finding may be edema (area of high signal intensity on fluid-sensitive sequences)

Plain radiography

Other Diagnostic Studies

X ray Chest

  • All patients should have initial radiography of chest and also repeated after an interval to detect complications of pyomyositis(like lung and cardiac complications).


  • Echocardiogram is used to diagnose cardiac complications of pyomyositis.


  • ECG is used to diagnose cardiac complications of pyomyositis.



The following conditions require immediate resuscitation:


Surgery is the mainstay treatment for pyomyositis.

  • Abscess drainage includes:

Medical Therapy


Appropriate analgesics are given when the patient presents with pain.

Antimicrobial therapy

  • Antimicrobial therapy is recommended for patients with pyomyocitis:[26]
  • Preferred regimen (3): Cefazolin 2 g IV q8h (if MSSA)
  • Alternate regimen: Vancomycin 1 g IV q12h (if MRSA)


Primary prevention

There are no primary preventive measures available for pyomyositis.

Secondary prevention

There are no secondary preventive measures available for pyomyositis.


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  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Chauhan S, Jain S, Varma S, Chauhan SS (2004). "Tropical pyomyositis (myositis tropicans): current perspective". Postgrad Med J. 80 (943): 267–70. PMC 1743005. PMID 15138315.
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  6. Drosos, Georgios. "Pyomyositis. A literature review." Acta Orthop Belg 71.1 (2005): 9-16.
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