Tuberculosis of sternum

Abstract

Skeletal tuberculosis is the result of haematogenous dissemination of bacilli following primary infection. Any bone in the body can be a site for tuberculosis. Cold abscesses of surrounding soft tissues with subsequent contiguous sinus tracts often occur. A painless cold abscess may be the only presenting clinical feature for a prolonged period. The tuberculin skin test is positive in 95% cases, pulmonary involvement occurs in about 50%. New imaging techniques with computed tomography (CT), magnetic resonance imaging (MRI), and CT-guided fine needle aspiration biopsy have revolutionized the diagnostic approach and have resulted in more accurate results and much less invasive procedures than plain radiography and open biopsy. Open biopsy enhances the chances for bacteriologic confirmation in upto 90% cases. Polymerase chain reaction (PCR) has been used as a potentially valuable technique in rapid diagnosis of musculoskeletal tuberculosis. However, a presumptive diagnosis can be made with the presence of caseous granulomas on histology. Surgical drainage of abscesses should be undertaken only if it cannot be controlled by aspiration and chemotherapy alone [1]. Case Report-1 A 30 year old non-smoker soldier had insidious onset symptoms of cough with expectoration, fever, anorexia and weight loss of one month duration. He also noticed a painless swelling over left lower scapular region a fortnight later. General physical examination was unremarkable. Chest examination revealed few crepitations in right infraclavicular region. Mantoux was 15 mm. Sputum smear was positive for acid fast bacilli (AFB). Chest radiograph revealed non-homogenous opacities in right upper zone. He was subjected to anti-tubercular treatment (ATT). After 2EHRZ he developed a cold abscess in the right parasternal region, which gradually enlarged and ruptured 4 months later to form a discharging sinus. After completing nine months ATT he developed another cold abscess at lower end of sternum, which too ruptured and left a discharging sinus. Three months later a third cold abscess developed over right 7th rib anterolaterally resulting in sinus later. At this time he was referred to us with a suspected diagnosis of drug resistant tuberculosis. On examination two ulcers with discharging sinuses over sternum measuring 5×7cm and 3×2.5cm, both with undermined edges and a third cold abscess over right 7th rib were evident (Fig-1). Fig. 1 Showing two ulcers with discharging sinuses over sternum both with undermined edges and a third cold abscess over 7th rib below right nipple Results of investigations revealed haemoglobin 9.8gm%, normal total and differential leucocyte counts. Sputum for acid-fast bacilli (AFB) was negative. His blood was negative for human immunodeficiency virus (HIV). Biochemical parameters were normal. Scraping from ulcers was negative for AFB. The cellular aspirate from cold abscess revealed necrotic material with cellular infiltrates comprising neutrophils, lymphocytes, macrophages along with epithelial cells, AFB were not seen on smear examination but pus culture grew Mycobacterium tuberculosis resistant to INH and Rifampicin (HR). Chest radiograph at this stage showed fibrocystic lesions at right upper zone and right mid zone and an erosive lesion over superior border of right 7th rib, erosion of sternum and soft tissue swelling over distal end of sternum. Ultrasonography showed a 15×35mm hypoechoic cystic area at lower end of sternum and a 30×20mm hypoechoic cystic region with debris behind sternum. CT confirmed erosion of anterior surface of sternum with adjacent soft tissue swelling and consolidation with infiltrative lesion in right lung. There was in addition pre and paravertebral abscess extending from D3 to D7 with erosion of D5 vertebra (Fig 2). Fig. 2 CT thorax showing erosion of sternum, vertebra with infiltrative lesion in right lung He was treated successfully with second line ATT comprising streptomycin, ethambutol, pyrazinamide, ethionamide and PAS with healing of all bony lesions and sinuses. Streptomycin was stopped after six months whereas rest of antitubercular drugs mentioned above were given for 18 months. No surgical intervention was done in this case.