A Rare Case of Extrapulmonary Tuberculosis in a Teenager

To the Editors: A 13-year-old boy of African descent presented with a 2-week history of progressively increasing right preauricular mass. The mass was associated with substantial pain upon mastication and nocturnal pain. Other symptoms were reduced appetite and 3-kg weight loss. Cough, fever and night sweats were not reported. Physical examination revealed slightly fluctuating swelling of the right temporomandibular joint (TMJ), in the absence of erythema, purulent discharge or facial nerve palsy. Biology showed microcytic anemia and inflammatory syndrome with high erythrocyte sedimentation rate. Medical history was unremarkable, and he tested negative for HIV. Computed tomography (CT)-scan of head and neck showed TMJ osteoarthritis and associated paratracheal lymph nodes, motivating the realization of a thoracic and mediastinal CT-scan. It revealed mediastinal necrotic lymph node as well as a parenchymal lesion (tree in bud) and a splenic lesion of 17 mm in diameter (Fig. 1).FIGURE 1.: A: Cervical CT-Scan: Partial destruction of the right condyle. B: Thoracic CT-Scan: Necrotic right-sided paratracheal, hilar and infracarinal lymph nodes and tree in bud lesion in the right upper lobe.At that time, tuberculosis (TB) disease was highly suspected, and after complete workup, classical quadrichemotherapy for TB was initiated. TB of the TMJ was confirmed by joint liquid as well as gastric lavage GeneXpert Mycobacterium tuberculosis-RIF and cultures. Culture-based first-line drug susceptibility testing revealed resistance to Pyrazinamide (PZA) only. Arthritis of the TMJ can have a traumatic, infectious, degenerative or inflammatory cause. Pain, swelling, limited movement and trismus’ sign are common findings. The clinical appearance of TB of the TMJ is nonspecific and may be similar to other etiologies.1 Diagnosis of osteoarticular TB in children is known to represent considerable diagnostic challenge due to nonspecific clinical manifestations and insidious disease course. Median diagnostic delay is several months. In addition, Mycobacterium tuberculosis smear and culture performance in children is poor.2 As osteoarticular TB usually involves the spine or large articulations, the diagnostic challenge was all the greater in this case, taking into account the rarity of TMJ involvement, with only a few cases reported in the literature. In our case, the stigmas of pulmonary TB on CT-scan, performed despite the absence of associated respiratory symptoms and signs, represented the key element pointing towards the diagnosis of TB in an early stage. In the pediatric population, destruction of the condyle results in mandibular growth disturbance and potential facial deformity; ankylosis may follow. The functional prognosis of the joint depends on the degree of destruction at the time of diagnosis and timing of treatment initiation, emphasizing the importance of early diagnosis.3 Finally, the patient’s African descent and the frequent ingestion of unpasteurized dairy products throughout his childhood, as well as the phenotypical monoresistance to PZA, were initially suggestive of Mycobacterium bovis as the causative agent. M. bovis intrinsic resistance to PZA is the consequence of a pcnA gene mutation but PZA monoresistance is not exclusive to M. bovis.4 This was illustrated by our case, as whole-genome sequencing was performed and detected wild-type Mycobacterium tuberculosis complex. Nevertheless, M. bovis should not be forgotten as a causative pathogen for osteoarticular TB, especially in the presence of PZA monoresistance.