In 1999, there were 7512 cases of tuberculosis (TB) notified in Hong Kong, 81 (1%) cases were reported in children aged less than 15 years old.¹ Classical systemic symptoms include fever, night sweats, anorexia, weight loss and malaise. Organ-specific symptoms include persistent cough, pleuritic pain, and haemoptysis.² The diagnosis of TB infection in children depends primarily on a high index of suspicion and appropriate investigations. It is suggested that TB infection should be considered in any child who has had a persistent cough and fever for more than two weeks unresponsive to antibiotic treatment.³ Around the world, almost 500 children die of tuberculosis (TB) infection every day. It has been estimated that 170,000 children die each year from the two most severe forms of disseminated disease, meningeal and miliary TB.⁴ In order to control the spread of TB, a high index of suspicion, accurate diagnosis, adherence to full course of treatment and contact tracing are all necessary. We report a child with pulmonary tuberculosis (PTB) that presented with a persistent cough for six weeks. The pulmonary tuberculosis was complicated by pleural effusion. The diagnosis of PTB was established by pleural biopsy.

Case report

WSF was a five-year old boy. He was born in Mainland China and came to Hong Kong three years ago. His parents claimed that his immunisation schedule was completed in China and Hong Kong though no Bacille Calmette-Guerin (BCG) scar was noticed. He enjoyed good past health and lived with his parents and elder brother in a 100-square-feet rented room in Shamshuipo. He presented with loss of appetite, malaise, night sweats, cough and low grade fever (oral temperature: 38) six weeks before admission. He attended the government general out-patient clinic and was treated as an upper respiratory tract infection (URTI) with symptomatic treatment. As symptoms persisted, he was brought to consult two private practitioners and was treated as URTI again. He was brought to the Accident & Emergency Department later as the fever and cough did not subside. He was admitted to hospital because of the left pleural effusion revealed by the chest radiograph (CXR).

Upon admission, he was lethargic. His temperature was 38.4 and oxygen saturation was 98% without any oxygen supplement. The physical findings were compatible with left pleural effusion. Erythrocyte sedimentation rate (ESR) was markedly raised to 106mm/hr and the Mantoux test was positive (12.5 x 10mm induration). PTB infection was suspected. Chest radiograph showed left pleural effusion with deviation of trachea to the right side (Figure 1). Chest drain insertion and pleural biopsy were done. Routine microscopy (R/M) of pleural fluid was negative. The fluid was exudative in nature, the acid-fast bacilli (AFB) smear and culture, cytology, polymerase chain reaction of Mycobacterium tuberculosis (TBPCR) were all negative. He was confirmed to have TB infection by pleural biopsy two days later. The histology of pleural biopsy showed granuloma with epithelioid macrophages, caseous necrotic centres and the Ziehl-Neelsen stain showed a few AFB. It was diagnostic of mycobacterial infection. The culture of pleura was also positive for Mycobacterium tuberculosis. Bronchoscopy was performed which revealed normal tracheo-bronchial tree without endobronchial lesion. Broncho-alveolar lavage (BAL) was negative for routine microscopy, AFB smear and M.tuberculosis culture, TBPCR. Early morning gastric lavage was negative for AFB smear, M.tuberculosis culture and TBPCR.

Figure 1: Chest radiograph showing left pleural effusion with deviation of trachea (arrow) to the right side.

Anti-TB drugs including isoniazid, rifampicin and pyrazinamide were prescribed for 6 months. Prednisolone was given for a month because of the presence of pleural effusion. The fever settled three days later. Chest drain was removed two weeks later with a total of 975ml of pleural fluid collected. Repeat CXR showed only minimal pleural effusion. There was no derangement of liver enzymes after the use of anti-TB drugs. The case was notified to the Department of Health and the whole family was referred to the Chest Clinic for family screening. Chest x-rays of his parents were normal. His elder brother had a positive Mantoux test with 20 x 21mm induration but there was no evidence of TB disease.

Discussion

This case illustrates the non-specificity of symptoms of TB infection and the importance of appropriate investigations for the diagnosis. The diagnosis of TB infection in children depends primarily on a high index of suspicion. Clinicians should be alert to the possibility of PTB when faced with a child who complains of persistent cough. In this case, the diagnosis would have been made earlier if proper physical examination, CXR, complete blood count including ESR and Mantoux Test had been performed earlier.

Pleural effusion is not uncommon in TB infection. By three months of pulmonary TB infection, 25% of cases developed a pleural effusion and by six months, there would be an effusion in 75% of cases.⁵ Effusions are usually unilateral but can be bilateral.⁶ Pleural effusion results from a hypersensitivity reaction to TB proteins and liposaccharides rather than microbial invasion of the pleura. Less than 10% of cases have positive AFB stain of pleural fluid as the bacilli seed from a subpleural pulmonary focus or a casesated lymph node. Culture of pleural fluid grew Mycobacterium tuberculosis in fewer than 65% of cases. In contrast, histological examination and culture of pleural tissue increase the diagnostic yield to between 80% and 90%.^7,8 Thus chest tapping coupled with pleural biopsy increase the yield of TB identification in pleural effusion. It was clearly demonstrated in this case as M.tuberculosis was only recovered in the pleural biopsy.

Conclusion

Medical practitioners should be aware of tuberculosis infection as a differential diagnosis when they encounter a child with persistent cough for more than two weeks. Pleural biopsy should be attempted before insertion of chest drain when tuberculosis infection is suspected.

Key messages

1. Pulmonary tuberculosis (PTB) is endemic in Hong Kong.
   
2. Anyone with chronic cough should be suspected to have PTB.
   
3. Chest radiograph and Mantoux test are important investigations for diagnosis of PTB.
   
4. Pleural biopsy should be taken in anyone with pleural effusion in which PTB is a possibility.