Unmasking tuberculous lymphadenitis in a middle-aged male with Hashimoto's thyroiditis: a case report.

Background: Tuberculous lymphadenitis (TBL), a form of extrapulmonary tuberculosis (TB), poses significant diagnostic challenges in primary care, especially when presenting atypically or in patients with underlying autoimmune disorders. Hashimoto's thyroiditis is an autoimmune condition characterised by hypothyroidism and may predispose individuals to opportunistic infections, including TB, due to immune dysregulation. The interplay between autoimmune diseases and TB is complex and not widely understood, particularly in non-endemic regions. This case highlights critical diagnostic considerations required in managing persistent cervical lymphadenopathy, especially in patients with autoimmune thyroiditis, highlighting the need for a systematic and vigilant diagnostic approach to diagnosis and management in primary care. Case Description: We present a 40-year-old Caucasian male with a background of Hashimoto's thyroiditis who initially sought medical care for flu-like symptoms, subsequently diagnosed as a viral upper respiratory tract infection. During examination, an incidental, painless, 3 cm cervical lymph node was identified, initially attributed to reactive viral lymphadenopathy. The patient exhibited no constitutional or respiratory symptoms, which may have contributed to diagnostic delay, particularly in a primary care setting less familiar with extrapulmonary TB, leading to initial conservative management. Three months later, the lymphadenopathy persisted and had increased to 4 cm in diameter, prompting further investigations. Blood tests revealed elevated inflammatory markers, normal thyroid function but elevated anti-thyroid peroxidase (anti-TPO) antibodies consistent with autoimmune thyroiditis. Neck ultrasound showed caseating lymphadenopathy suggestive of TB, and subsequent positive QuantiFERON-TB testing and fine-needle aspiration cytology confirmed the diagnosis of TBL. The patient was successfully treated with a 6-month regimen of anti-tuberculous therapy, achieving complete clinical resolution. Conclusions: This case underscores the diagnostic complexity associated with TBL in patients with autoimmune diseases such as Hashimoto's thyroiditis. It highlights the necessity for maintaining a broad differential diagnosis for unexplained lymphadenopathy in primary care, particularly when classical symptoms of TB are absent. Primary care clinicians should adopt a proactive approach to persistent lymphadenopathy, including timely escalation to advanced diagnostic tests, to avoid diagnostic delays, ensure timely initiation of effective treatment, and prevent disease progression and potential transmission.