SAT-309 - A Rare Cause of Adult Suppurative Thyroiditis: Thyroid Abscess from Infected Branchial Cleft Cyst

Background

Acute suppurative thyroiditis (AST) as a syndrome is typically caused by hematogenous spread of bacteria, especially in immunocompromised patients, but can also be caused by pyriform sinus defects [1]. Branchial cleft cysts, which are congenital neck anomalies, can be a less common cause of AST through the contiguous spread of bacteria from the oral cavity across the tract to the thyroid. This report presents a rare case of AST in a young adult caused by a fourth branchial cleft cyst with airway compromise. This is important to recognize, as it may be mistaken for subacute thyroiditis or typical AST, both of which differ in management.

Case Presentation

A 25-year-old male presented with several days of worsening left-sided neck swelling and pain, dysphagia, fevers, anxiety, and insomnia. Examination revealed left-sided neck tenderness, thyroid enlargement, and a hoarse voice. Initial laboratory studies demonstrated a WBC count of 16.7 x 10³/µL, ESR of 80 mm/hr, and CRP of 279.5 mg/L; TSH was 0.281 µIU/mL, free T4 was 2.7 ng/dL, and free T3 was 6.6 pg/mL. CT neck imaging revealed a 7 cm x 3.1 cm heterogeneous area of the left thyroid with septations and retropharyngeal edema concerning for AST with abscess and related to a fourth branchial cleft cyst. Fine-needle aspiration grew Fusobacterium necrophorum. The patient was treated with IV antibiotics, several days of propranolol, and intermittent steroids for retropharyngeal edema, which required incision and drainage (I&D) with temporary drain placement. The patient’s thyroid function normalized, fevers and leukocytosis resolved, and he was discharged home with outpatient ENT evaluation for definitive surgical management of his fourth branchial cleft cyst.

Discussion and Conclusion

The thyroid gland is typically resistant to bacterial infection due to its protective capsule, lymphatic drainage, vascular supply, and iodine content, especially in immunocompetent individuals [2]. Because of this, contiguous spread of infection, which can be caused by congenital neck anomalies, is uncommon and may have a delayed diagnosis. Similar conditions that may be confused with AST due to bacterial spread from a branchial cleft cyst include subacute thyroiditis and more typical AST due to hematogenous spread. Unlike subacute thyroiditis, this patient’s symptoms only transiently improved with steroids, and unlike typical AST, surgical intervention is required to prevent recurrent infection. This case highlights the importance of considering branchial cleft cysts as non-thyroidal sources of infection in patients with unilateral thyroiditis. Early recognition is crucial to guide appropriate antimicrobial and surgical management.

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