PRIMARY THYROID TUBERCULOSIS: A RARE CASE REPORT

Thyroid tuberculosis (TT) is a rare form of extrapulmonary tuberculosis caused by infection of the thyroid gland by Mycobacterium tuberculosis . Although uncommon in the general population, extrapulmonary tuberculosis is more prevalent in individuals with HIV, occurring mainly in pleural, lymph node, meningeal, pericardial, and osteoarticular forms. Thyroid involvement is uncommon, possibly due to intense vascularization, high iodine concentration, and the colloid environment, which hinder bacillary survival. Diagnosis is challenging because clinical and imaging findings are nonspecific and often mimic neoplasms or other thyroiditis. Confirmation usually requires culture or biopsy of thyroid tissue. Male patient, 41 years old, HIV-positive, attended an infectious diseases outpatient clinic on 08/26/2024 with persistent evening fever, myalgia, and 10 kg weight loss over three weeks. He had used azithromycin for the previous five days, with partial improvement. Given the hypothesis of fever of unknown origin, laboratory and imaging tests were requested. Chest CT showed thyroid heterogeneity, and ultrasound revealed a hypercaptating nodule associated with TSH suppression and glandular hyperfunction. The IGRA test was positive, confirming, together with other findings, the diagnosis of thyroid tuberculosis. The patient started treatment with rifampicin, isoniazid, pyrazinamide, and ethambutol. After two months, there was clinical improvement and weight gain, allowing transition to rifampicin and isoniazid therapy, completing six months of treatment with complete remission of symptoms. In this case, the immunocompromised patient presented nonspecific systemic symptoms and thyroid alterations compatible with TT, including a hypercaptating nodule and hormonal dysfunction. The positive IGRA test, together with the clinical picture, supported the diagnosis. Conventional antitubercular therapy was effective, with good clinical response. Treatment is usually medical, with surgery reserved for abscesses, suspicion of neoplasm, or therapeutic failure. Prognosis is generally favorable with adequate treatment. TT, although rare, should be considered in cases of thyroid nodules or dysfunction in immunosuppressed patients, highlighting the importance of an integrated diagnostic approach and early therapy.