Spontaneous Hemorrhagic thyroid cyst presenting as unilateral painful thyroiditis in primary care: early recognition of a potentially life-threating complication.

Spontaneous hemorrhage within a thyroid nodule is an uncommon but potentially alarming condition presenting with acute neck pain, swelling, and compressive symptoms that may threaten the airway and pose diagnostic and management challenges. We describe a 35-year-old Asian woman who presented with sudden onset of severe left-sided neck pain and swelling, accompanied by dysphagia and exertional dyspnea. There was no history of trauma, anticoagulant use, or prior thyroid intervention. Physical examination revealed marked unilateral thyroid tenderness and swelling without overt airway compromise. Thyroid function tests were within normal limits. Neck ultrasonography demonstrated a complex mixed solid-cystic left thyroid nodule measuring 3.2 × 2.4 × 3.5 cm with internal echogenic septations, consistent with a hemorrhagic thyroid cyst. Initial conservative management with non-steroidal anti-inflammatory drugs provided minimal relief. The patient was subsequently treated with a short course of high-dose oral corticosteroids and underwent ultrasound-guided fine-needle aspiration, yielding 7 mL of dark brown hemorrhagic fluid. Cytological examination revealed macrophage-predominant cyst contents with no evidence of malignancy. Significant symptomatic improvement was noted following aspiration and steroid therapy. The patient was referred for endocrinology follow-up, with elective hemithyroidectomy discussed due to the potential risk of recurrence. Spontaneous hemorrhage of a thyroid nodule, although rare, should be considered in patients presenting with acute unilateral neck pain and swelling, even in the absence of identifiable risk factors. Early imaging, vigilant airway assessment, and individualized management are crucial. In clinically stable patients, conservative treatment with aspiration and corticosteroids may be effective, while surgical intervention should be reserved for recurrent cases or those with airway compromise. This case highlights the critical role of primary care physicians in early recognition and urgent referral of rare but potentially life-threatening thyroid conditions presenting with acute neck swelling.