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Year : 2006  |  Volume : 9  |  Issue : 2  |  Page : 113-115

Tropical pyomyositis: Clinical and MR imaging characteristics

1 Departments of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS) (Deemed University), Bangalore - 560 029, India
2 Departments of Neuroimaging and Interventional Neuroradiology, National Institute of Mental Health and Neurosciences (NIMHANS) (Deemed University), Bangalore - 560 029, India
3 Departments of Neuromicrobiology, National Institute of Mental Health and Neurosciences (NIMHANS) (Deemed University), Bangalore - 560 029, India

Correspondence Address:
Sanjib Sinha
Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Hosur Main Road, Bangalore - 560 029, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-2327.25984

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We report a 19-year-old man who presented with 2 weeks history of fever, myalgia, swelling of the face and body and raised serum CK level. Following partial response to steroids, he deteriorated clinically. On admission, he had an ill look, hepatomegaly, muscle weakness and multiple, fluctuant and non-tender subcutaneous swellings of variable size, over the right forearm and left thigh. Diagnostic procedures revealed it to be tropical pyomyositis due to staphylococcus aureus. He improved completely with parenteral cloxacillin. Reporting of such cases will increase awareness.

Keywords: MRI, Staphylococcus aureus , tropical pyomyositis

How to cite this article:
Sinha S, Taly A B, Jerrry J, Nagarathna S, Singhal A K, Shobha N. Tropical pyomyositis: Clinical and MR imaging characteristics. Ann Indian Acad Neurol 2006;9:113-5

How to cite this URL:
Sinha S, Taly A B, Jerrry J, Nagarathna S, Singhal A K, Shobha N. Tropical pyomyositis: Clinical and MR imaging characteristics. Ann Indian Acad Neurol [serial online] 2006 [cited 2022 Sep 25];9:113-5. Available from:

  Introduction Top

Pyomyositis is a subacute, deep, bacterial infection of muscle and soft tissues, most commonly caused by Staphylococcus aureus.[1] It is commonly encountered in tropical countries and forms about 1-4% of surgical admissions in some series.[2],[3] Diagnosis is often missed especially during the early stages, due to its decreasing incidence, unfamiliarity, atypical presentations, lack of specific signs, antibiotic abuse and wide range of differential diagnosis. Muscle imaging modalities like ultrasound and MRI often assist in the diagnosis.[1],[4]

We report the clinical and laboratory profile and interesting MR imaging observations of an immuno-competent patient with tropical pyomyositis (TPM) and discuss the diagnostic delays and it's implications.

  Case Report Top

A 19-year-old man presented with a 2 week's history of fever, myalgia and swelling of the face and body. The serum CPK level was elevated (740 IU/L, Normal: 20-170 IU/L). He was treated with steroids along with antibiotics, based on a possibility of "Viral myositis". He reported partial remission of pain and swelling. During the recovery phase, he developed headache, recurrent vomiting and drowsiness. He was then referred to our center. There was no history of seizures and visual, bulbar and sphincter dysfunction, high colored urine and muscle trauma. Past history was insignificant. Family history was non-contributory. He was a manual laborer, did not use alcohol, tobacco or illicit substance, did not have high-risk behavior or did not recently travel to the western hemisphere.

He was febrile, looking ill and had pallor. There was tachycardia with raised jugular venous pulses and crepitations on the right side of chest, anteriorly. Liver was mildly enlarged, firm and non-tender. There were multiple, fluctuant and non-tender subcutaneous swellings of variable size (average 2 x 3 cm) over the right forearm and left thigh. However, there was no redness or raised temperature. He was conscious and oriented to person, time and place. Cranial nerves were normal. There was generalized muscle tenderness. Muscle power was normal with normal stretch reflexes. Plantar response was flexor.

He had low hemoglobin of 8.2 gm%, raised WBC count of 18,000/cu. mm with neutrophilic dominance (90%), rapid ESR at first hour (76 mm/hr) and low serum albumin of 2.2 gm%. Blood sugar, electrolytes and renal and hepatic function tests were within normal limits. Serum CPK at admission was 806 IU/L (normal up to 160 IU/L). Serum RA factor, ANA, LE cell phenomena, HbsAg, VDRL and HIV were negative, but CRP was positive. ECG revealed sinus tachycardia. Chest X-ray detected right-sided pleural effusion. Thigh and forearm X-ray did not reveal calcification. Ultrasound examination showed mild liver enlargement. A minimal enlargement of ventricles was noted in the CT scan of brain. However, CSF examination was normal (protein - 22 mg%, glucose - 38 mg% and nil cells).

Ultrasound examination of muscles showed multiple areas of altered echotexture and morphology. There were multiple compartments noted in the muscles of legs, thighs, upper limbs and back. These were hypoechoic and compressible, but without any subcutaneous collection. MRI study of muscles revealed multiple hypointense swelling on T1W images, which were enhancing at the periphery on gadolinum injection. These were hyperintense on T2W images [Figure - 1]a, b, c. Drainage of these abscesses from right forearm showed thick yellowish green pus under pressure. There were gram-positive cocci in clusters. Growth on culture media detected Staphylococcus aureus and was sensitive to common antibiotics including cloxacillin. Blood culture also grew S. aureus with similar sensitivity pattern.

A diagnosis of tropical pyomyositis (TPM) was considered and he was treated with parenteral cloxacillin for 2 weeks. He improved significantly during his stay in hospital. He was lost to follow up.

  Discussion Top

Tropical pyomyositis was first described by Scriba in 1885.[1],[5] It is called by various other terms like myositis tropicans, tropical skeletal muscle abscess and tropical myositis.[6] Levin et al in 1971 reported the first case from a temperate region[2] and since then, many cases have been reported from various geographical regions of the world.[7],[8] Although the classical presentation is with muscle abscess, the hallmark of the disease is not an abscess, but evidence of myositis on a biopsy specimen of the involved muscle. Non-tropical pyomyositis might affect people with AIDS, malignancy, uncontrolled diabetes, dermatomyositis or any debilitating illnesses.[1]

Young adult males are most susceptible and present with localized infection of muscle.[1],[9] Initially there is myalgia with fever and then painful, firm swelling appears, followed by wooden texture-like abscess. Multiple abscesses are more common.[10] Precipitating factors are muscle trauma, nutritional deficiencies and parasitic infections. Large muscles are commonly involved and include quadriceps, glutei, pectoralis major, serratus anterior, biceps, iliopsoas, gastrocnemius and abdominal and spinal muscles.[1] There are three stages of TPM: invasive, suppurative and late. The invasive stage consists of sub-acute onset of fever, painful firm swelling with or without erythema and minimal constitutional symptoms. Most patients present in the suppurative stage in the 2nd or 3rd week when abscesses form and they have high fever and severe systemic symptoms. Classical signs of abscess like fluctuation and erythema may be absent. In the late stage, dissemination of infection occurs, resulting into bactermia, septicemia, toxic shock syndrome and metastatic abscess.[1] Our patient presented with features of pain and swelling, appearing early in the course (Invasive stage), followed by suppurative stage and associated with sepsis, during which time he was referred to us.

The commonest organism is S. aureus.[1] Following any previous blunt muscle trauma, seeding of infection occurs during transient bacteremia. It is believed to be related to defective phagocyte function and T-lymphocyte defect against S. aureus. Interestingly, muscle abscesses are rare in staphylococcal septicemia. Diagnosis is often missed, especially during the early stages due to its decreasing incidence, unfamiliarity with this entity, atypical presentations, lack of early specific signs and a wide range of differential diagnosis.[1],[9]

The diagnosis should be suspected in the setting of HIV infection, diabetes, leukemia, renal failure, asplenia, scleroderma, rheumatoid arthritis and use of immuno-suppressive drugs and chemotherapy and can be supported by presence of anemia, leucocytosis, raised ESR and acute phase reactants. Blood cultures might grow organisms in 5-10% in tropical regions and in 20-30% in temperate regions. Muscle enzymes may be normal or slightly raised despite muscle destruction.[1] Ultrasound examination reveals hypoechoic areas with increase muscle bulk.[11] CT scan shows areas of low attenuation with loss of muscle planes and surrounding rim of enhancement. MRI detects hypo-intense lesion with hyper-intense rim on T1W, which enhances on contrast injection. These are hyperintense on T2 WI. MRI is superior to CT and USG in detection and characterization of lesions.[11],[12],[13],[14] The characteristic imaging features are reported during the suppurative stage. A muscle biopsy or aspiration of pus with culture and sensitivity, clenches the diagnosis.

It is important to have a high index of suspicion and familiarity with the clinical and imageological features of this imminently treatable entity.

  References Top

1.Chauhan S, Jain S, Varma S, Chauhan SS. Tropical pyomyositis (myositis tropicans): Current perspective. Postgrad Med J 2004;80:267-70.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Levin MJ, Gardner P, Waldvogel F. Tropical pyomyositis: An unusual infection due to Staphylococcus aureus. N Engl J Med 1971;24:196-8.   Back to cited text no. 2    
3.Horn CV, Master S. Pyomyositis tropicans in Uganda. E Afr Med J 1968;45:463-71.   Back to cited text no. 3  [PUBMED]  
4.Pretorious ES, Hruban RH, Fishman EK. Tropical pyomyositis: Imaging findings and review of literature. Skeletal Radiol 1996;25:576-9.  Back to cited text no. 4    
5.Traquair RN. Pyomyositis. J Trop Med Hyg 1947;50:81-9.   Back to cited text no. 5    
6.Cheidozi LC. Pyomyositis: Review of 205 cases in 112 patients. Am J Surg 1979;137:255-9.   Back to cited text no. 6    
7.Gibson RK, Rosenthal SJ, Lukert BP. Pyomyositis: Increasing recognition in temperate climates. Am J Med 1984;77:768-72.   Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Hall RL, Callaghan JJ, Moloney E, Martinez S, Harrelson JM. Pyomyositis in a temperate climate, presentation, diagnosis and treatment. J Bone Joint Surg Am 1990;72:1240-4.  Back to cited text no. 8  [PUBMED]  
9.Uribe-Flores JD, Hernandez-Jacome M. Tropical pyomyositis. A report of 188 cases. Gac Med Mex 2004;140: 607-10.  Back to cited text no. 9  [PUBMED]  
10.Malhotra P, Singh S, Sud A, Kumari S. Tropical pyomysitis-Experience of a tertiary care hospital in North West India. J Assoc Physic India 2000;48:1057-60.   Back to cited text no. 10  [PUBMED]  
11.Trusen A, Beissert M, Schultz G, Chittka B, Darge K. Ultrasound and MRI features of pyomyositis in children. Eur Radiol 2003;13:1050-5.   Back to cited text no. 11  [PUBMED]  [FULLTEXT]
12.Soler R, Rodriguez E, Aguilera C, Fernandez R. Magnetic resonance imaging of pyomyositis in 43 cases. Eur J Radiol 2000;35:59-64.   Back to cited text no. 12  [PUBMED]  [FULLTEXT]
13.Yuh WT, Schreiber AE, Montgomery WJ, Ehara S. Magnetic resonance imaging of pyomyositis. Skeletal Radiol 1988;17:190-3.   Back to cited text no. 13    
14.Meena AK, Rajashekhar S, Reddy JJ, Kaul S, Murthy JM. Pyomyositis-clinical and MRI characteristics report of three cases. Neurol India 1999;47:324-6.  Back to cited text no. 14    


[Figure - 1]

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