Discussion:
Tuberculosis is a chronic infectious disease caused by M. tuberculosis. Every year, around ten million people are diagnosed with tuberculosis. Despite being a preventable and curable disease, it the world’s top infectious killer. (2) The main risk factors for developing tuberculosis infection are poverty, undernutrition, diabetes, smoking, and immunocompromised conditions, namely, human immunodeficiency virus infection (HIV). (4)
The lungs are the primary site for tuberculosis infection, with various presentations including primary TB, reactivation TB, endobronchial TB, and tuberculoma. (4) The main pulmonary tuberculosis symptoms are fever, cough, difficulty breathing, anorexia, weight loss, and night sweats. However, in the advanced stage and the absence of proper treatment, complications may occur in the form of hemoptysis, pneumothorax, bronchiectasis, and extensive pulmonary destruction. (5)
Extrapulmonary tuberculosis refers to TB involving organs other than the lungs (e.g., pleura, lymph nodes, abdomen, genitourinary tract, skin, joints, bones, or meninges). It represented 15% of the 7.0 million incident cases notified in 2018, and the most typically reported sites were lymph node, pleura, and urogenital tuberculosis. (6)
Skeletal tuberculosis accounts for 2-6 % of all tuberculous infections, with the spine being the most commonly affected site. The chest wall involvement and ribs in skeletal tuberculosis are exceptionally uncommon, accounting for < 5% of bone and joint TB. It is twice more common in males than females, with typical age between 15-30 years, as in our patient. (7)
TB abscesses of the chest wall are usually seen at the sternum margins and along the rib shafts. Three mechanisms have been described as responsible for the chest wall involvement, including a direct extension from the pleural or parenchymal disease, hematogenous dissemination, or lymphatic extension. (8) In our case, although the patient does not have any respiratory symptoms with no parenchymal involvement, the hilar and mediastinal lymph nodes enlargement with peripheral enhancement and central necrosis as seen on chest CT scan represents the possible focus for the chest wall involvement.
Chest wall tuberculosis usually presents insidiously as swelling and pain over the bone, with few constitutional symptoms, making the diagnosis difficult and delayed in most cases, averaging 4-28 months. Some patients may present with secondary infection complications, spontaneous fractures of the ribs or sternum, and compression or erosion of the large blood vessels. (9) Differential diagnosis of the chest wall swellings includes granulomatous diseases (sarcoidosis, Non-Tuberculosis mycobacterium), chronic infections (fungal or parasitic), and benign or malignant growth (fibrous dysplasia, osteoblastoma, chondral tumors, malignant bony or cartilaginous tumors, and metastasis). (10) Our patient presented with fourth months history of slow-growing and painful anterior chest wall masses, weight loss, and anorexia with no evidence of complications.
The laboratory investigations for diagnosing chest wall TB are non-specific, including slightly raised inflammatory markers (C-reactive protein, wight blood cells, and serum ferritin), anemia of chronic disease, which were the same as found in our case. (11) The imaging modalities useful in chest wall TB are radiography, Ultrasound, and CT scan. The findings from these modalities help determine the degree of thoracic cage involvement and give a hint for the possible focus of involvement in the form of pleural, parenchymal, and mediastinal lymph nodes abnormalities. (12) Although the Magnetic Resonance Imaging (MRI) of the chest provides a lot of information about the soft tissues and degree of extension of the abscess; CT chest is considered the investigation of choice by many authors; as it is easily accessible, affordable, and provides detailed information almost as MRI chest. Typical CT findings in the chest wall TB include bone destruction, soft tissue masses crossing the fascial planes, with abscess and calcification, and underlying pleuro-parenchymal tubercular involvement. (12,13) There is an increasing role for the Ultrasound to help localize the affected areas and the size of the collections. The abscesses usually appeared as hypoechoic areas, with varying degrees of internal heterogeneity. Bone fragments appeared as echogenic foci within these hypoechoic collections. (14)
Fine-needle aspiration (FNA) of the chest wall collection represents a simple, non-invasive way to get the diagnosis of tuberculosis. The aspirated material is usually sent for acid-fast bacilli (AFB) smear, PCR, and culture. The yield of AFB smear is low as it needs many bacteria; on the other hand, PCR requires a small number of bacteria and can detect drug resistance. In addition to identifying the sensitivity to the specific treatment, AFB cultures provide the advantage of knowing the organism species to exclude the Mycobacteria other than tuberculosis as a well-known cause of chest wall infections (11,15). In our patient, PCR and culture confirmed the diagnosis of Mycobacterium Tuberculosis (MTB) with full sensitivity to first-line anti-TB medications.
There is no consensus on the optimal treatment of chest wall tuberculosis. The general role is for the medical treatment, in the form of anti-tuberculosis medications, with a six-month regimen being sufficient in most cases. Surgical intervention may be needed in cases of extensive tissue damage, the presence of draining sinuses, or failure of medical treatment. (16,17)