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Decoding the Masquerader: A multi-organ tour of Melioidosis from radiology to reality!
Case Study
Wed Apr 09 2025
Decoding the Masquerader: A multi-organ tour of Melioidosis from radiology to reality!
This case series has been contributed by Dr Sharadhini Karanth – from KH Manipal.
{This was selected as an educational exhibit at the European Congress of radiology and received widespread appreciation}.
CLINICAL CONTEXT
Melioidosis is an infectious disease caused by the Gram-negative bacterium Burkholderia pseudomallei. This environmental saprophyte is commonly found in soil and stagnant water in tropical and subtropical regions. The organism can enter the human body through skin abrasions or wounds, inhalation of contaminated dust, or ingestion of contaminated water [1]. Individuals with compromised immune systems, such as those with diabetes, chronic alcoholism, renal or liver failure, or malignancies, are at significantly higher risk of infection.
The disease is geographically expanding, with cases reported in new endemic regions, highlighting the growing global health concern. The signs and symptoms are non-specific and overlap with several diseases, including tuberculosis. Thus melioidosis, ‘the great mimicker’ of many diseases, is grossly underdiagnosed and underreported across the tropics, including India[2]. Melioidosis presents with a wide spectrum of radiological manifestations, ranging from localized abscesses to systemic involvement of multiple organs, including the lungs, liver, spleen, kidneys, and central nervous system. The variability in presentation underscores the critical
importance of correlating imaging findings with clinical history and laboratory results to achieve accurate diagnosis and effective disease management.
Results or Findings
The most common site for melioidosis infection is the lung, followed by the spleen and liver. Other organs such as kidney, prostate, brain and musculoskeleton can also be involved. [1]
PULMONARY MELIOIDOSIS
Chest radiography is useful for diagnosis [2]. However CT scans of the chest can give more detailed information.
Pulmonary melioidosis predominantly presents as pneumonia, accounting for nearly half of reported cases [3]. Radiologically, it often manifests as upper lobe infiltrates with or without cavitation. Acute forms may show diffuse nodular infiltrates or discrete lobar consolidations, with septicemic cases favoring upper lobes and non-septicemic cases affecting lower lobes.3. Subacute and chronic forms progress slower, with mixed nodules, patchy opacities, and minimal fibrosis. Differentiation from tuberculosis can be challenging.
Fig 1: In a culture proven case of melioidosis, an axial section of CT in a lung window shows multiple scattered nodules.
Fig 2: Contrast enhanced CT scan of a proven case of melioidosis showing a cavitary lesion with an air-fluid level in the apico-posterior segment of the left upper lobe s/o lung abscess.
Fig 3: Coronal sections of the CT thorax show multiple patchy areas of consolidations.
Though melioidosis spares the lung apex, less fibrosis, absence of pleural effusion with no mediastinal lymphadenopathy, and presence of confluent consolidation go more in favor of melioidosis1. Pleural effusions, empyema, pneumothorax, and hydropneumothorax are rare but possible complications, often linked to cavity rupture5.
VISCERAL MELIOIDOSIS
Spleen
The spleen is the most commonly affected extrapulmonary visceral organ in melioidosis. Splenic lesions are typically multiple, small, and discrete, ranging from 0.5 to 1.5 cm. Larger multiloculated lesions, subcapsular collections, and perisplenic extensions may also occur [4]. Splenic abscesses, more frequent in melioidosis than other infections, can present as microabscesses or large multiseptate lesions. Imaging findings include hypoechoic lesions on ultrasound and hypodense lesions on CT scans. A characteristic “target sign” or “bull’s eye” lesion may be seen, and larger abscesses may demonstrate a honeycomb or necklace sign 6. Splenic vein thrombosis
and infarcts are additional complications in systemic melioidosis.
Liver
Hepatic melioidosis shares similar radiological characteristics with splenic involvement, often presenting as single or multiple abscesses. These lesions range from small hypoechoic microabscesses to large multiloculated and multiseptate abscesses 1. Larger abscesses, exceeding 2 cm, may display a honeycomb or necklace sign
Fig 4: Axial and coronal sections of contrast enhanced CT showing a multiloculated abscess in the right lobe of the liver.
on imaging, particularly on ultrasound and CT scans. The simultaneous presence of hepatic and splenic abscesses is highly suggestive of melioidosis, especially in patients with comorbidities or a history of travel to endemic regions. Differentiation from other infections, such as tuberculosis or fungal abscesses, is often required due to overlapping imaging features 1.
Fig 5: In a known case of metastatic Ca breast, on chemotherapy presented with fever. Fig a shows variable sized lung nodules, Fig b shows ill defined hypodense lesion in segment VII of liver (marked with star) and multiple hypodense lesions in spleen (marked with arrow). Blood culture isolated B. pseudomallei and treated with intravenous meropenem. Follow up scan Fig c, d shows significant decrease in the lung nodules, resolution of liver lesion and significant decrease in the splenic lesion.
Pancreas
Pancreatic melioidosis is less common and usually occurs as part of multiorgan involvement. CT imaging reveals multifocal microabscesses or focal large abscesses, predominantly in the pancreatic body. Associated findings may include surrounding inflammation, splenic vein thrombosis, and peripancreatic fat stranding. 3
Kidneys
Varies from multiple ill-defined or well defined hypodensities, rim enhancing fluid collections, abscesses, and pyelonephritis. Involvement is more often bilateral and multiple rather than a localized or unilateral disease.5
Prostate
Manifests as abscesses, predominantly in the peripheral zone, detectable via CT or ultrasound imaging.
MUSCULOSKELETAL MELIOIDOSIS
Involvement is seen in 5–48% of cases [5] , manifests as osteomyelitis, septic arthritis, synovitis, or soft tissue abscesses
Fig 6: Intramedullary altered signal intensity of the femur with cortical breachforming irregular abscess collection within the vastus lateralis and intermedius muscle extending to subcutaneous plane, from which a sinus tract extend and reach to the skin surface.
Fig 7: Case of septic arthritis, culture proven Melioidosis. Fig a, b, c sagittal sections of T2 , PDFS and post contrast sequences shows multiple irregular peripherally enhancing intercommunicating hyperintense on T2WI collections in visualised portion of shaft of femur and proximal tibia. Knee joint effusion noted extending into supra patellar bursa showing peripheral post contrast enhancement (marked with arrow).
Fig 8: Axial and coronal sections of contrast enhanced CT scan of the neck shows multilobulated predominantly hypoattenuating mass showing peripheral contrast enhancement, extending under the left sternocleidomastoid muscle, from the posterior cervical space to the submandibular space anteriorly, involving the regions of the II and III lymph nodes levels, displacing the structures of the carotid and pharyngeal spaces medially and the left submandibular salivary gland anteriorly. Incision and drainage was done. Culture sensitivity showed Burkholderia cepaciae and treated with inj Meropenem 1g for 10 days.
It often affects weight-bearing joints (knee, hip, ankle) and bones via hematogenous spread or adjacent infection. Imaging reveals joint effusion, bone erosion, and abscesses, with MRI being the most sensitive modality for diagnosis. 3
NEUROLOGICAL MELIOIDOSIS
Affecting only 4% of cases3, presents significant challenges due to its high mortality rate and severe morbidity among survivors. The radiological manifestations of neurological melioidosis encompass diverse findings, with rim-enhancing lesions and leptomeningeal enhancement being most characteristic. While imaging may be normal or show non-specific changes, key features include abscess formation, meningoencephalitis, brainstem encephalitis, transverse myelitis, paraspinal collections, and sinonasal involvement. Brain parenchymal disease can manifest as both micro and macro-abscesses with encephalitic features.
Fig 9: Intra-axial T2/ FLAIR hyperintensities noted along bilateral corticospinal tracts involving subcortical and deep white matter of bilateral frontal (right> left), left parietal lobes showing patchy areas of diffusion restriction, patchy areas of pseudonormalization on ADC and post contrast enhancement, s/o encephalitis/cerebritis.
CONCLUSION
Melioidosis is a significant public health concern due to its increasing endemicity and ability to mimic other infections and involve multiple organs. Awareness of these radiological patterns, coupled with clinical history such as septicemia or travel to endemic regions, is crucial for early diagnosis. Recognizing these features allows for timely and appropriate management, preventing complications of this versatile and potentially fatal infection.
References
- Amin, Dhanush, Sridevi Chinta, Anu Kapoor, M. V. S. Subbalaxmi, D. Amulya Reddy, A. Neelima, and Jyotsna Yarlagadda. “Imaging Case Series of Melioidosis: The Great Masquerader.” Egyptian Journal of Radiology and Nuclear Medicine 54, no. 1 (February 27, 2023): 44. https://doi.org/10.1186/s43055-023-00994-2.
- Mohapatra, Prasanta R., and Baijayantimala Mishra. “Burden of Melioidosis in India and South Asia: Challenges and Ways Forward.” The Lancet Regional Health - Southeast Asia 2 (July 1, 2022). https://doi.org/10.1016/j.lansea.2022.03.004.
- Wanaporn Burivong, Sunsiree Soodchuen, Panitpong Maroongroge, Prasit Upapan, and Vichit Leelasithorn. “Radiographic Manifestations of Melioidosis: A Multi-Organ Review.” Medical Research Archives, Radiographic Manifestations of Melioidosis: A Multi-organ Review, 5, no. 3 (March 2017).
- Dhiensiri, T., S. Puapairoj, and W. Susaengrat. “Pulmonary Melioidosis: Clinical-Radiologic Correlation in 183 Cases in Northeastern Thailand.” Radiology 166, no. 3 (March 1988):711–15. https://doi.org/10.1148/radiology.166.3.3340766.
- Alsaif, Hind S., and Sudhakar K. Venkatesh. “Melioidosis: Spectrum of Radiological Manifestations.” Saudi Journal of Medicine & Medical Sciences 4, no. 2 (2016): 74–78. https://doi.org/10.4103/1658-631X.178286.
- Currie, B. J., D. A. Fisher, D. M. Howard, J. N. Burrow, D. Lo, S. Selva-Nayagam, N. M. Anstey, et al. “Endemic Melioidosis in Tropical Northern Australia: A 10-Year Prospective Study and Review of the Literature.” Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America 31, no. 4 (October 2000): 981–86. https://doi.org/10.1086/318116.
- Ong, Sidney Ching Liang, Mina Mustafa Mahmood Alemam, Nor Aniza Zakaria, and Nur Azidawati Abdul Halim. “Honeycomb and Necklace Signs in Liver Abscesses Secondary to Melioidosis.” BMJ Case Reports 2017 (October 19, 2017): bcr2017222342, bcr-2017–222342. https://doi.org/10.1136/bcr-2017-222342.
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Figure 1: Karyotype of 45,X/46,X,i(X),(q10)
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Figure 2: Isochromosome formation
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CONCLUSION:
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The received wisdom on testing for DL and TL status is that samples must be subjected for cytogenetic FISH based testing as it is more reliable and specific for these targets, and the same is incorporated into routine clinical practice.
As is wont to happen in non hospital based settings, the patient was referred to a tertiary care referral centre and lost to follow up.
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CLINICAL DETAILS
A 44-year-old female presents with a history of multiple episodes of giddiness. The patient reports noticing swelling within her oral cavity, specifically in the area posterior to the right tonsillar pillar for 6 months. On clinical examination, there is no palpable swelling in the neck. However, a significant parapharyngeal swelling, approximately 4x4 cm in size, is observed in the oral cavity posterior to the right tonsillar pillar. This swelling is associated with a deviation of the uvula to the left. The clinical findings suggest a possible mass or lesion in the parapharyngeal space, warranting further investigation to determine the underlying aetiology.
IMAGING FINDINGS:
MRI reveals a well-defined, oval-shaped lesion in the right carotid space, measuring 3x4x5 cm. The lesion causes splaying of the internal and external carotid arteries and extends medially into the right parapharyngeal space. The lesion is iso to hyperintense on T1/T2WI and shows homogeneous postcontrast enhancement.
CT angiography of neck and brain showed the above-mentioned lesion to be hypoenhancing in the arterial phase.
The differential diagnoses considered were carotid body tumour, cervical sympathetic chain schwannoma and vagal schwannoma. Vagal schschwannomas displace the carotid arteries anteriorly rather than splaying them. Cervical sympathetic chain schwannomas displace the carotid arteries anteriorly but occasionally splay the internal and external carotid arteries without encasement. Carotid body tumours are usually pulsatile in nature, show multiple internal flow voids, splay and encase the carotid arteries, and show intense early enhancement followed by rapid washout. However, in our case, the mass showed progressive enhancement. Hence, in the given clinical setting and after reviewing the radiological features, a probable diagnosis of schwannoma was made.
FOLLOW-UP
Patient underwent surgery and it was found to be arising from the hypoglossal nerve and the biopsy revealed schwannoma.
DISCUSSION
Here are the possible causes of Lyre sign and the imaging features:
CONCLUSION
The ‘Lyre’ sign describes the characteristic splaying of the carotid artery bifurcation due to a carotid body tumour on conventional carotid angiography. This sign, however, is not diagnostic of carotid body tumours. An accurate diagnosis is, therefore, essential before embarking on invasive procedures such as biopsy or aspiration to prevent potential catastrophe.
As this case exemplifies, the road to a definitive diagnosis demands a synthesis of clinical acumen, imaging finesse, and sometimes, surgical intervention.
Bottomline: “Not all that splays is carotid body tumor”!!
Dr Adarsh Ishwar Hegde
KH site, Manipal
