A Case of Chylothorax

Abstract

INTRODUCTION: Chylothorax is uncommon and it is an even rarer manifestation of Mycobacterium tuberculosis. We report a case of chylothorax and a review of the literature. CASE PRESENTATION: A 32-year-old female nurse from Myanmar who have been working in a private nursing home in Singapore for 2 years presented with non-productive cough for 10 days, fever for 3 days and 2-kg weight loss over 1 month prior to admission. There was no significant past medical history. On examination, she was febrile with reduced air entry in the right hemithorax. There were palpable inguinal lymph nodes bilaterally. Chest X-ray showed a moderate right pleural effusion. Blood tests showed mild lymphopenia (0.54x10 and 9 cells/L), elevated C-reactive protein (54.8 mg/L) and transaminitis (ALT 180 U/L, AST 278 U/L) but normal total bilirubin (6 I1/4mol/L). Sputum Ziehl-Neelsen smear was negative. A chest tube was inserted and milky white pleural fluid was drained. Pleural fluid analysis showed elevated protein (49 g/L) with lymphocyte predominance (97%), numerous mesothelial cells (2+) and adenosine deaminase level of 31.1 U/L. Pleural fluid triglyceride and cholesterol level were 10.9 mmol/L (965 mg/dL) and 2.0 mmol/L (77 mg/dL) respectively. Pleural culture and PCR were negative for Mycobacterium tuberculosis. Thoraco-abdominal CT scan showed a large right pleural effusion with no mediastinal lymphadenopathy, enlarged ovaries with ascities and retroperitoneal lymphadenopathy. Serum Ca 125 level was 1219 U/mL. HIV screen was negative. Differential diagnoses of lymphoma, ovarian carcinoma and tuberculosis were considered. Inguinal lymph node biopsy showed non-caseating granulomatous inflammation with negative Ziehl-Neelsen stain. Empirical anti-tuberculous therapy was not initiated due to transaminitis. The employer and the patient decided to repatriate for further management after a total of 26 inpatient days as the insurance cap was met. Three weeks later, sputum culture grew isoniazid-resistant Mycobacterium tuberculosis complex. The sputum culture report was forwarded to the patient in Myanmar. DISCUSSION: Chylothorax is suspected when the pleural fluid has a milky appearance and is diagnosed when the pleural fluid triglyceride level exceeds 110mg/dL. A literature search revealed 10 published cases of chylothorax associated with tuberculosis over the past 20 years including non-English publications. Most of the case reports described chylothorax occuring with extensive intrapulmonary disease or mediastinal lymphadenopathy. In this case, chylothorax was the sole intrathoracic finding. There was only a single paper reporting a case with no thoracopulmonary abnormalities detected on thoracic CT scan (1). The accumulation of chylothorax may be due to obstruction of lymphatic flow at a microscopic level. This case presented a diagnostic challenge due to the lack of intrapulmonary manifestation of tuberculosis. Furthermore, the pleural fluid showed numerous mesothelial cells. Previous studies have concluded that the presence of numerous mesothelial cells in exudative pleural effusion makes the diagnosis of tuberculosis highly unlikely (2). The abundance of mesothelial cells may be explained by the difference in the pathogenesis process of chylothorax compare to tuberculous effusion. The findings on the CT scan of the abdomen (enlarged ovaries, retroperitoneal lymphadenopathy) and elevated serum Ca 125 level further complicate the clinical picture. Peritoneal tuberculosis has been reported to mimic advanced ovarian carcinoma with the appearance of adnexal mass and elevated serum Ca 125 level (3). We believe the abdominal findings were due to tuberculosis. CONCLUSION(S): Tuberculosis is a rare cause of chylothorax especially in the absence of mediastinal lymphadenopathy. The presence of numerous mesothelial cells in pleural effusion does not exclude the diagnosis of tuberculosis. Peritoneal tuberculosis can mimic ovarian carcinoma. Tuberculosis should be considered a differential diagnosis of chylothorax especially if the patient comes from an endemic country.