Unmasking malignancy-thyrotoxic hypokalemic periodic paralysis and papillary thyroid carcinoma in a young male with Graves' disease: a case report.

Background: Thyrotoxic hypokalemic periodic paralysis (THPP) is a rare complication of hyperthyroidism, most often associated with Graves' disease. It is characterized by transient muscle weakness and hypokalemia due to an intracellular potassium shift. Although Graves' disease is also associated with an increased risk of thyroid nodularity and, in some cases, malignancy, the co-occurrence of THPP and papillary thyroid carcinoma (PTC) remains exceedingly rare. To our knowledge, this is only the second reported case documenting the simultaneous presence of all three conditions: THPP, Graves' disease, and PTC. Case Description: A 26-year-old male with a known history of Graves' disease presented with acute flaccid paralysis due to THPP. This episode led to thyroid imaging, which revealed thyroid nodules and cervical lymphadenopathy. Fine-needle aspiration (FNA) was suspicious for malignancy. The patient underwent total thyroidectomy with central and left neck dissections, with final pathology confirming multifocal PTC, including a widely invasive follicular variant, and regional lymph node metastases. Conclusions: This case illustrates the rare triad of THPP, Graves' disease, and PTC. In this patient, an episode of THPP served as the clinical trigger that led to further thyroid evaluation and ultimately the diagnosis of an aggressive and multifocal thyroid malignancy. It emphasizes the need for thorough thyroid evaluation in patients with Graves' disease who present with THPP, as an underlying malignancy may be present. Early imaging, cytologic assessment, and surgical consultation should be considered.