A Rare Case of Tuberculous Pleural Effusion Diagnosed by Ziehl Neelson Stain

Mycobacterium tuberculosis is the etiologic agent of tuberculosis which remains the leading cause of mortality, internationally. It commonly affects the lungs but can also infect other parts of the body. Extra pulmonary tuberculosis (EPTB) includes lymphatic, pleural, skeletal, ocular, endometrial, pancreatic, genitourinary, cerebral, and meningeal or military tuberculosis. In India EPTB, particularly of Pleural cavity is reported rarely. Pleural effusion is an excessive accumulation of fluid in the pleural cavity which, in normal condition, contains a relatively small amount of fluid-approximately 10 ml on each side. The idea of this article is to diagnose TB of pleural cavity by Ziehl Neelson staining, which usually presents with fever, weight loss and cough.


Introduction
Tuberculosis (TB) remains a leading public health problem across the world, with approx. 9 million new cases and 1.5 million TB deaths every year [1]. India stays to have the highest number of TB cases in the world, with over 2 million active TB cases which accounts for 25% of international TB burden every year [2]. Even though reliable data from India are lacking, 15-20% of all TB is extra pulmonary. Extra pulmonary tuberculosis (EPTB) is defined as occurrence of TB in parts of the body other than the lungs. Other types of EPTB are lymphatic, pleural, skeletal, central nervous system, pleural, ocular, endometrial, pancreatic, genitourinary, miliary and cerebral tuberculosis. The prevalence of EPTB is higher in HIV co infected patients and children [3].
Here, we report a case of Tuberculosis of pleural cavity diagnosed after one month of complain of respiratory symptoms. The patient had cough and weight loss for one month.

Case Presentation
A male patient of 26-years, non-diabetic, normotensive, native from Jharkhand, admitted with the complaints of cough and fever for 1 month with increased weight loss since 6 weeks. Patient was HIV negative (by ELISA) with no past history or exposure of tuberculosis infection. Patient also had no family history of tuberculosis, Diabetes, Hypertension.
Patient was conscious cooperative but ill looking. On examination patient was febrile, BP-110/70. His physical examination was suggestive of left pleural effusion. So the patient was investigated with chest X-ray which indicated significant flat air and left pleural effusion ( Figure 1). Complete investigations with different parameters were done to diagnose the cause of Pleural effusion. All lab reports were within normal range except pleural Adenosine deaminase (188.6 U/l),Total count (12400), Serum uric acid (1.5), serum creatinine (0.5), serum alkaline phosphate (225U/l), LDH (18,2030 U/l ( Table 1).
After all aseptic precaution, thoracocentesis was done on left side and 560 ml of pus like fluid drained. The fluid was investigated for Microbiological, cytological and biochemical analysis ( Table 2)

Discussion
Pleural effusion is second most common extra pulmonary tuberculosis next to tuberculosis lymphadenitis. About 20% cases of extra pulmonary tuberculosis presented with pleural effusion [4].
Most literatures supports that, MTB is the most common cause (66%) of pleural effusion followed by malignancy (18%) and parapneumonic Effusion (10%) [5]. Now a days, diagnosis of pleural effusion by MTB is frequently done by clinical, radiological, histological, and laboratory findings. Latest techniques like liquid culture (Bactac/MGIT), nucleic acid probes, polymerase chain reaction (Gen Xpert) have increased the probability for diagnosing TB earlier.
But the gold standard for the diagnosis of Tuberculosis Pleural Effusion (TPE) will remain the detection of Mycobacterium tuberculosis (MTB) in pleural fluid, or pleural biopsy specimens, either by microscopy and/or culture, or the histological demonstration of caseating granulomas in the pleura along with acid fast bacilli. Supportive evidence like demonstration of classical TB granulomas in the pleura and elevated adenosine deaminase (ADA), lactate dehydrogenase (LDH) and alkaline phosphates levels in pleural fluid do help. Baba et al. demonstrated that ADA is a reliable marker of pleural TB in HIV-positive patients, even for those with low CD4 counts, while Chung et al. confirmed that ADA is an accurate marker in renal transplant recipients. On the contrary, raised ADA levels may be observed in a number of conditions potentially leading to a false positive diagnosis of TB which includes rheumatoid effusion, empyema due to other bacteria, mesothelioma, lung cancer, parapneumonic effusion, and haematological malignancies. Pleural fluid analysis will remains an important tool in patients of pleural effusion.

Conclusion
Though it requires a lot of patience and examination of at least 300 fields under oil immersion microscope to visualize acid fast bacilli in clinical samples but still, ZN stain is a very strong method to diagnose TB in resource constraint lab . In addition to that, ADA values >70 U/L are highly supportive of tubercular etiology in pleural fluid even if it is high in many other conditions. Chest X-ray also helps in diagnosis of TPE. Thus to conclude, pleural effusion in India needs to be studied deeply and differently because of more prevalence of tuberculosis in India. The screening of Pleural fluids by ZN stain in resource constraint settings can provide good results despite low yield.