Differential Diagnosis

The patient presents with neck swelling, palpitations, heat intolerance, and increased sweating, which are suggestive of a thyroid disorder. The following differential diagnoses are considered:

• Single most likely diagnosis
  • Thyroiditis (De Quervain's thyroiditis): The patient's symptoms of neck swelling, pain, and odynophagia, along with a recent history of viral infection, support this diagnosis. The absence of weight loss, tremors, and exophthalmos also points towards thyroiditis.
• Other Likely diagnoses
  • Graves' disease: Although the patient has a family history of Graves' disease, the absence of exophthalmos, lid retraction, and tremors makes this diagnosis less likely. However, the presence of tachycardia and heat intolerance cannot be ignored.
  • Toxic multinodular goiter: The patient's thyroid gland is enlarged and symmetrically palpable, which could be consistent with a toxic multinodular goiter. However, the absence of a palpable thrill or audible bruit makes this diagnosis less likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Thyroid storm: Although the patient's symptoms are not severe enough to suggest a thyroid storm, it is essential to consider this diagnosis due to its high mortality rate. The presence of tachycardia, heat intolerance, and increased sweating could be indicative of a thyroid storm.
  • Medullary thyroid carcinoma: The patient's neck swelling and pain could be indicative of a thyroid malignancy. Although this diagnosis is less likely, it is crucial to consider it due to its potential severity.
• Rare diagnoses
  • Riedel's thyroiditis: This rare form of thyroiditis is characterized by a hard, fibrotic thyroid gland that can cause compressive symptoms. Although the patient's thyroid gland is enlarged, it is not hard or fibrotic, making this diagnosis less likely.
  • Pituitary thyroid axis abnormality: An abnormality in the pituitary-thyroid axis, such as a thyroid-stimulating hormone (TSH)-secreting pituitary adenoma, could cause the patient's symptoms. However, this diagnosis is rare and would require further investigation to confirm.

Investigation and Management

To confirm the diagnosis, the following investigations are recommended:

• Thyroid function tests (TFTs) to assess TSH, free thyroxine (FT4), and free triiodothyronine (FT3) levels
• Thyroid antibodies to rule out autoimmune thyroiditis
• Ultrasound of the thyroid gland to assess its size and structure
• Fine-needle aspiration cytology (FNAC) if a thyroid nodule is suspected

Management of the patient will depend on the confirmed diagnosis. If thyroiditis is confirmed, the patient may be treated with anti-inflammatory medications and beta blockers to manage symptoms. If Graves' disease or toxic multinodular goiter is diagnosed, the patient may require antithyroid medications, radioactive iodine, or surgery.