Pediatric Orbital Tuberculosis: Highlighting the Role of Zoonotic Exposure

To the Editors: Orbital tuberculosis (O-TB) is a rare form of extrapulmonary TB that may mimic neoplasms, inflammatory pseudotumors, or abscesses. Diagnosis relies on microbiology, PCR, histopathology and imaging. Despite challenges, outcomes are favorable with timely antitubercular therapy, usually involving isoniazid, rifampicin, pyrazinamide and ethambutol for 6–12 months. Drug resistance and surgical needs in complicated cases underline the importance of early recognition and multidisciplinary management.1 Although preventive measures have lowered zoonotic TB in developed countries, distinguishing Mycobacterium bovis and M. caprae from M. tuberculosis is difficult due to overlapping clinical and radiological findings. Thus, zoonotic TB remains underrecognized, and careful history-taking is essential.2 The natural pyrazinamide resistance of M. bovis also affects treatment planning. We report a rare pediatric case of TB with ocular involvement, underscoring the need to consider zoonotic TB in differential diagnosis and to strengthen surveillance measures.3 A previously healthy 15-year-old male presented with a 1-year history of multiple cervical lymphadenopathies and a 6-month history of left-sided ptosis, tearing, intermittent diplopia and blurred vision. His medical history revealed that he was a refugee working as a shepherd, and one of his animals had died from tuberculosis about 1 year ago. Family history was unremarkable, and there were no symptoms of fever, cough, weight loss or headache. His vaccinations were reportedly complete. On physical examination, multiple lymph nodes were palpated: 2 × 0.5 cm firm mobile nodes in the left cervical and submandibular regions, a 2 × 0.5 cm fluctuant node over the SCM muscle, and a 0.5 × 0.5 cm firm preauricular node. Ophthalmologic examination showed ptosis partially covering the left pupil, but no other pathology. A BCG vaccination scar was present. Other systemic examination was normal. Neck ultrasonography revealed multiple lymphadenitis lesions with the largest measuring 6.5 mm × 17 mm, showing peripheral inflammation and necrotic areas. Laboratory investigations including complete blood count, liver and renal function tests were normal; acute phase reactants were negative. HIV test was nonreactive. Chest radiograph and abdominal ultrasound were unremarkable. Tuberculin skin test (Purified protein derivative (PPD)) was 17 mm, and Interferon-gamma release assay (IGRA) was positive. Acid-fast bacilli smear, Polymerase chain reaction (PCR) and culture from induced sputum were negative. Family screening for TB revealed no index case. Orbital and cranial magnetic resonance imaging demonstrated thickening and enhancement of the left optic nerve, hyperintense fluid-attenuated inversion recovery (FLAIR) signals with mild diffusion restriction involving the anterior orbital septum, superior tarsal plate, eyelid and lacrimal gland, consistent with granulomatous infection (Fig. 1). Additionally, two hyperintense FLAIR foci with contrast enhancement were noted in the intraconal and prechiasmatic segments of the left optic nerve, suggestive of optic neuritis. Cerebrospinal fluid examination was unremarkable, and cerebrospinal fluid acid-fast bacilli smear, PCR and culture were negative.FGURE 1.: Before treatment: increased FLAIR signal of the left optic nerve (A) and subtle enhancement on postcontrast T1WI (B). On axial FLAIR sequence and precontrast T1WI, preseptal soft tissue thickening (C) and increased FLAIR signal (D) are observed, while axial postcontrast T1WI demonstrates increased enhancement within the thickened soft tissue (E). T1WI indicates T1-weighted imaging.Excisional biopsy of a cervical lymph node revealed necrotizing granulomatous lymphadenitis with caseous necrosis and Langhans-type giant cells. Immunological evaluation excluded chronic granulomatous disease or other immunodeficiencies. Based on clinical history, positive PPD and IGRA, histopathological findings and radiologic evidence of granulomatous involvement of the optic nerve, eyelid and lacrimal gland, the patient was started on standard 4-drug anti-TB therapy (isoniazid, rifampicin, pyrazinamide and ethambutol) along with oral prednisolone (40 mg/day), tapered off over 6 weeks. After 2 months, treatment was continued with isoniazid and rifampicin. The temporal association between the onset of symptoms and the death of his animal suggested possible zoonotic transmission, although microbiologic evidence could not be obtained. Since the patient responded well to standard therapy, with significant clinical and radiological regression, treatment was not modified. Follow-up examinations showed complete resolution of ptosis, diplopia and blurred vision (Fig. 2). One-year follow-up orbital magnetic resonance imaging demonstrated complete resolution of previously noted orbital lesions (Fig. 3). Given optic nerve involvement at presentation, antitubercular treatment was continued for 12 months before discontinuation. Tuberculosis remains a major global health problem, with extrapulmonary involvement in up to 20% of cases. Ocular TB is rare (3%–5%), especially in children, and its nonspecific features often delay diagnosis.4 Reported manifestations include epibulbar masses, uveitis, keratitis and conjunctivitis, sometimes mimicking tumors.5,6 In our case, the optic nerve, lacrimal gland and eyelid were affected, with full recovery achieved after multidisciplinary care and antitubercular therapy. Zoonotic TB, caused mainly by M. bovis and M. caprae, remains underrecognized as it is clinically indistinguishable from M. tuberculosis. Transmission risk is higher in children with animal contact or exposure to unpasteurized dairy. In our patient, zoonotic transmission was suspected due to occupational history and livestock TB.7 In conclusion, this case highlights rare pediatric ocular TB and the need to consider zoonotic transmission in differential diagnoses, emphasizing detailed history-taking and strengthened surveillance in high-risk populations.FGURE 2.: After treatment: resolution of left preseptal thickening and contrast enhancement is observed on T2-weighted and postcontrast T1-weighted images (A, B). On axial T2, signal abnormality of the left optic nerve has resolved, and postcontrast T1WI shows disappearance of enhancement (C, D).FGURE 3.: Clinical appearance of the left eyelid before and after treatment.