Pyomyositis, also referred to as myositis tropicans, typically manifests as an inflammatory suppuration in skeletal muscles because of bacterial infection of the muscle tissue [1]. Pyomyositis occurs more often in the tropical climate. Patients from temperate regions are scarce and typically develop pyomyositis because of an ongoing immunosuppressive therapy, a proven diabetes mellitus background, or due to HIV infection [2]. In most cases, Staphylococcus aureus is the causative infectious agent. Streptococci from groups A, B, C, and G as well as pneumococci, Gram-negative bacilli, and Haemophilus bacteria have been reported in rare cases [3]. Bacterial infection can occur after a mechanical trauma such as a fall or a traffic accident [3] [4].

Pyomyositis symptoms develop slowly. Patients often suffer from diffuse and unspecific early manifestations like fever, myalgia, swelling, and tenderness. Later on, redness of the skin area and increased warmth of the skin above the affected muscle may occur. Reports have indicated that quadriceps, biceps, iliopsoas, gastrocnemius, pectoralis major, serratus anterior, abdominal, gluteal, and spinal muscles are more prone to be affected by pyomyositis [5] [6]. Pyomyositis can affect both genders and all age groups, however, an increased incidence has been reported in males (overall male to female ratio - 1.5: 1), particularly in young males [5]. The death can occur if the infection is untreated [4].

• Myopathy

  Multifocal pyomyositis is a rare inflammatory myopathy caused by bacterial infection and abscess formation in multiple skeletal muscles. To date, electromyography (EMG) of pyomyositis has not been reported. [ncbi.nlm.nih.gov]

  ) muscular dystrophies and myopathies ( G71 - G72 ) myopathy in amyloidosis ( E85.- ) myopathy in polyarteritis nodosa ( M30.0 ) myopathy in rheumatoid arthritis ( M05.32 ) myopathy in scleroderma ( M34.- ) myopathy in Sjögren's syndrome ( M35.03 ) [icd10data.com]

• Myalgia

  Pyomyositis is a pyogenic infection of the skeletal muscles causing myalgia and fever in patients. Hematogenous seeding engendered by persistent bacteremia and septic embolism is usually the underlying cause of the disease. [ncbi.nlm.nih.gov]

  Our patient highlights the importance of obtaining a travel history and an early MRI in the evaluation of unexplained myalgias and severe muscle tenderness. [shmabstracts.com]

  Patients often suffer from diffuse and unspecific early manifestations like fever, myalgia, swelling, and tenderness. Later on, redness of the skin area and increased warmth of the skin above the affected muscle may occur. [symptoma.com]

  Mental Health and Neurosciences (NIMHANS), Hosur Main Road, Bangalore - 560 029, Karnataka India Source of Support: None, Conflict of Interest: None DOI: 10.4103/0972-2327.25984 We report a 19-year-old man who presented with 2 weeks history of fever, myalgia [annalsofian.org]

• Muscle Tenderness

  Her physical examination showed muscle tenderness and woody induration. Laboratory tests revealed anemia, increased acute phase reactants and normal muscle enzymes. [ncbi.nlm.nih.gov]

  Clinical Presentation FEVER, LOCALIZED CRAMPY MUSCLE PAIN, SWELLING • 3 clinical stages • Greater than 90% of patients present with stage 2: occurs 10-21 days after onset of symptoms and can be characterized by fever, exquisite muscle tenderness, edema [slideshare.net]

  Our patient highlights the importance of obtaining a travel history and an early MRI in the evaluation of unexplained myalgias and severe muscle tenderness. [shmabstracts.com]

  Stage 2 is referred to as the “purulent stage” [2], occurring 10 to 21 days after the initial onset of symptoms and patients present with fever, severe muscle tenderness, and increased edema. A frank abscess may be clinically present [4]. [hindawi.com]

• Thigh Pain

  A 6-year-old boy presented with right buttock and thigh pain following a mild fever and sore throat. The pain worsened, and he became unable to walk. On admission, his temperature was 38.4 C. [ncbi.nlm.nih.gov]

• Muscle Swelling

  Renal failure Immunosuppression Clinical Features More commonly affects proximal lower extremity muscles First stage Localized muscle pain, low grade fevers, vague complaints[2] Localized muscle inflammation without abscess Second stage Worsening pain, muscle [wikem.org]

  Imaging Electromyography Short duration, low amplitude polyphasic potentials Ultrasonography First imaging investigation usually Characteristic features are Muscle swelling; Hypoechoic areas in the muscle belly Heterogenous hypoechoic areas Hyperechoic [boneandspine.com]

   Computed tomography (CT) is helpful for detecting muscle swelling and well-delineated areas of fluid attenuation that display rim enhancement with contrast, as well as for radiographic-guided drainage of purulent material. 5/31/2015 23 Radiography [de.slideshare.net]

  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 [wikidoc.org]

• Neck Swelling

  On admission, he was febrile with unilateral neck swelling. Random blood glucose was normal and an HIV test negative. CT imaging confirmed a large heterogeneous mass extending throughout the entirety of the left sternocleidomastoid muscle. [ncbi.nlm.nih.gov]

The first suspicion of pyomyositis can be formulated on the basis of the patient's history. If the patient has recently traveled to tropical countries, has been involved in a traffic accident, or is being treated with immunosuppressive agents, further investigations are indicated to validate the suspicion. Blood laboratory tests are typically too unspecific but may be used for cross-checking purposes. Elevated white blood cell counts, particularly peripheral blood eosinophils, together with normal serum creatine kinase (CK) are often found in pyomyositis patients [7] [8]. Blood cultures can reveal a bacterial infection [9].

The gold standard for a final diagnosis is provided by computed tomography (CT) or magnetic resonance imaging (MRI), which can pinpoint the exact locations of the suppurative inflammation in the affected muscles [10]. A muscle biopsy may also be ordered to prove edema in early pyomyositis or necrotic degenerations with abundant inflammatory cells in advanced pyomyositis [5] [10]. Pus aspiration and analysis will help identify the causative bacteria and guide further management and treatment. In the minority of cases, the analyzed pus can be sterile [11].

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