Abstract
Tuberculosis (TB) of the thyroid gland, either in its primary or secondary form, is an extremely rare occurrence. It is infrequent even in countries with high incidence and prevalence of pulmonary and extrapulmonary TB. We report here a case of primary tuberculosis of thyroid presenting to us with sudden onset thyroid swelling since 20 days.
1
Introduction
Extrapulmonary tuberculosis has been on the rise both in endemic and in non endemic countries over the past few years. However, TB of the thyroid gland still remains extremely infrequent, with only about 200 cases reported so far, including in endemic countries like India . The prevalence varies from 0.1% to 0.6% in histologically diagnosed specimens, including areas with endemic TB. Secondary TB thyroid is more common, with bacilli reaching the gland via hematogenous, lymphatic route or directly from larynx or cervical tuberculous nodes. Primary TB is much rarer. Since these patients usually present with a diffuse or localized thyroid swelling, a differential of thyroid TB takes a backseat in favor of other common entities like multinodular goiter, neoplasia, thyroglossal cyst or lymphoma . Many of these remain asymptomatic and thus Fine Needle Aspiration Cytology (FNAC) or histopathological examination of the resected specimen forms the mainstay of diagnosis .
2
Case description
A 54 year old lady presented with complaint of painless progressive swelling in the region of thyroid since the past 6 months. She was clinically euthyroid with no compressive symptoms of dysphagia or dyspnea. There was no relevant past medical history of pulmonary or extrapulmonary TB. Family history was also insignificant for TB. Clinical examination revealed bilateral nodular and firm thyroid enlargement with right lobe measuring 2 × 2 cm and left lobe measuring 3 × 2 cm. There was no cervical lymphadenopathy. Bilateral vocal cords were symmetrically mobile with good airway on flexible fibreoptic laryngoscopy. Serum FT3 86.87, FT4 5.7, TSH 2.35 and other routine blood investigations were within normal limits. Chest X ray was normal. Ultrasound of the neck showed right lobe thyroid to be measuring 2.5 × 2.2 × 3.2 cm and left lobe 2.4 × 2.9 × 3.2 cm. Bilateral multiple hypoechoic nodules were seen, the largest measuring 1.8 × 1.5 cm in left lobe, suggestive of multinodular goiter. A Fine Needle Aspiration Cytology (FNAC) was done showing benign follicular epithelial cells with few Hurthle cell changes. There were many polymorphs and few lymphocytes, suggestive of subacute thyroiditis. The patient underwent total thyroidectomy for cosmetic reasons and specimen was sent for histopathological examination. The gross specimen was grayish white with grayish brown normal areas. Tissue showed multiple granulomas of epitheloid cells, Langhans giant cells, lymphocytes and plasma cells with central caseous necrosis and follicles with oncocytic changes ( Figs. 1 and 2 ). No definite acid fast bacilli were seen on Ziehl–Neelsen stain. Biopsy was hence suggestive of granulomatous thyroiditis due to tuberculosis. Postoperative ESR was 100, and CT of the chest was negative for pulmonary tubercular changes. Patient has been started on Anti Tubercular Treatment (ATT) with isoniazid, rifampicin, ethambutol and pyrazinamide along with thyroxine 110 μg daily and is currently on regular follow up.
