Case Study

Thoracic melioidosis: A diagnostic dilemma

Asian Cardiovascular & Thoracic Annals 2015, Vol. 23(2) 219–220 ß The Author(s) 2014 Reprints and permissions: DOI: 10.1177/0218492314521823

Omer Ashraf1, Anand Iyer1, Ramya Krishnan2 and Sumit Yadav1

Abstract The diagnosis of melioidosis can be difficult, and it is frequently described as ‘‘the great mimicker’’. We report a case of thoracic melioidosis presenting as a mediastinal mass with impending superior vena cava obstruction. With the presumptive diagnosis of mediastinal tumor, the patient underwent surgery for tissue sampling, and a purulent collection was found. The clinical syndromes of melioidosis and the diagnostic dilemma are discussed.

Keywords Anti-bacterial agents, burkholderia pseudomallei, melioidosis, northern Territory, vena cava, superior

Introduction Melioidosis is caused by the organism Burkholderia pseudomallei, a Gram-negative bacterium present in soil and surface water. The disease is endemic in Northern Australia and South East Asia.1 The spectrum of presentation can range from acute sepsis to more chronic disease; most often, it involves the lungs and intraabdominal organs but could present anywhere. Risk factors for infection include diabetes, hazardous alcohol intake, and chronic renal disease.2 The incubation period of acute disease is between 1 and 21 days.3 However, latent infections with presentation delayed for months or years have also been described.3 Lymphadenopathy may present as necrotic nodes and mimic tuberculosis or malignancy, when it tends to cause a diagnostic dilemma.

Case report A 51-year old indigenous woman from Far North Queensland presented to a rural hospital with rigors, dyspnea, pleuritic chest pain, and nonproductive cough. Her past medical history included type 2 diabetes mellitus and smoking. Routine blood tests showed leukocytosis with neutrophilia, elevated erythrocyte sedimentation rate and C-reactive protein, with poor glycemic control. A chest radiograph revealed right upper lobe consolidation consistent with pneumonia. She was subsequently admitted and

treated with intravenous antibiotics with a good result. Over the following month, she presented multiple times with low-grade symptoms. A follow-up chest radiograph showed a right superior mediastinal mass, prompting concern for underlying malignancy. At bronchoscopy, the right upper lobe apical segment bronchus was obstructed by edematous tissue. Transbronchial biopsy, brushings and washings were all negative for malignancy. Chest computed tomography confirmed a right superior mediastinal mass with associated superior vena cava compression (Figure 1). The patient had developed mild dysphagia but did not have signs of superior vena caval syndrome. Endoscopic fine-needle aspiration biopsy was then performed, but the result was again inconclusive for malignancy. In view of the patient’s dysphagia and impeding superior vena caval obstruction, a referral to thoracic surgery was made. We initially performed a videoassisted thoracoscopy, but the right upper lobe was adherent to the mediastinum, necessitating conversion to a minithoracotomy. A large abscess was identified and drained, and a chest tube was inserted 1 Department of Cardiothoracic Surgery, Townsville Hospital, Queensland, Australia 2 Department of Radiology, Townsville Hospital, Queensland, Australia

Corresponding author: Omer Ashraf, MBBS, Department of Cardiothoracic Surgery, Townsville Hospital, 100 Angus Smith Drive, Douglas, Queensland 4814, Australia. Email: [email protected]

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Asian Cardiovascular & Thoracic Annals 23(2)

Figure 1. Computed tomography showing a mediastinal melioid mass narrowing the superior vena cava.

intraoperatively. The chest tube was removed a few days later in the ward. Culture of operative specimens was positive for Burkholderia pseudomallei, confirming the diagnosis of melioidosis. Histopathology showed no evidence of malignancy. The patient was treated with intravenous meropenem for 4 weeks and continued to improve. The patient was discharged home on an additional 4 weeks of oral cotrimoxazole. Repeat imaging showed resolution of the mediastinal mass.

Discussion Transmission of melioidosis occurs through ingestion, inhalation, or inoculation via exposure of wounds to contaminated soil or water.1 Histopathological findings include necrotizing inflammation, abscess or granuloma formation, with multinucleated giant cells,4 occasionally mimicking tuberculosis.5 Successful culture from clinical specimens remains the diagnostic gold standard; however, a polymerase chain reaction has shown early promise, being particularly sensitive when taken from a direct specimen.1,6 Variations in clinical presentation and severity may be due to virulence factors of various bacterial strains, host immune response, and mode of transmission.7 Ceftazidime, carbapenems, and amoxicillin-clavulanate are the backbone of initial therapy. Maintenance therapy typically comprises oral cotrimoxazole with or without doxycycline.6 Clinical syndromes can be categorized as bacteremic or nonbacteremic, with bacteremic patients having a higher risk of mortality (21%–37% vs. 4%).3 The mortality rate for melioidosis with associated septic shock has been reported as 20%–80%.3 In their study of

melioidosis cases over 20 years in Darwin, Currie and colleagues8 found that 85% of cases were acute and occurred within 2 months of transmission, 11% were chronic infections presenting after 2 months, and 4% were reactivation of latent melioidosis. Pneumonia is the most common presentation (50%). Other forms of infection include prostatic abscess, parotitis, skin and soft tissue infections, and encephalomyelitis.7 Various radiological patterns of thoracic melioidosis have been recognized. Acute disseminated infection is characterized by multiple lung nodules or multilobar consolidation with subsequent formation and rupture of cavities, leading to pneumothorax or bronchopleural fistula. Subacute or chronic localized infection follows an insidious course and manifests as lobar, segmental consolidation, patchy opacities or migrating opacities. This case demonstrates the importance of considering melioidosis as a possible diagnosis in the setting of a mediastinal mass with chronic infective symptoms, and an important nonmalignant cause of superior vena caval syndrome. The blood cultures were negative. In such cases, tissue biopsy and culture cinches the diagnosis and ensures prompt management. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflicts of interest statement None declared. References 1. Dance DA. Melioidosis: the tip of the iceberg [Review]? Clin Microbiol Rev 1991; 4: 52–60. 2. Currie BJ, Fisher DA, Anstey NM and Jacups SP. Melioidosis: acute and chronic disease, relapse and re-activation. Trans R Soc Trop Med Hyg 2000; 94: 301–304. 3. Currie BJ, Fisher DA, Howard DM, et al. Endemic melioidosis in tropical northern Australia: a 10-year prospective study and review of the literature [Review]. Clin Infect Dis 2000; 31: 981–986. 4. Saravu K, Vishwanath S, Kumar RS, et al. Melioidosis—a case series from South India. Trans R Soc Trop Med Hyg 2008; 102(Suppl 1): S18–S20. 5. Vidyalakshmi K, Chakrapani M, Shrikala B, Damodar S, Lipika S and Vishal S. Tuberculosis mimicked by melioidosis. Int J Tuberc Lung Dis 2008; 12: 1209–1215. 6. Leelarasamee A. Recent development in melioidosis. Curr Opin Infect Dis 2004; 17: 131–136. 7. Cheng AC and Currie BJ. Melioidosis: epidemiology, pathophysiology and management [Review]. Clin Microbiol Rev 2005; 18: 383–416.

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Thoracic melioidosis: a diagnostic dilemma.

The diagnosis of melioidosis can be difficult, and it is frequently described as "the great mimicker". We report a case of thoracic melioidosis presen...
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