Late-Onset Episodic Weakness With Hyperkalemia Suggestive of Hyperkalemic Periodic Paralysis

A rare late-onset presentation of episodic weakness associated with hyperkalemia is described in a 72-year-old male with concurrent early-stage chronic lymphocytic leukemia. He experienced frequent episodes of generalized muscle weakness accompanied by loss of speech, shortness of breath, and fatigue, with a documented serum potassium level of 6.5 mmol/L obtained within 30 minutes of an attack. Treatment with acetazolamide and dietary modification was associated with a substantial reduction in episode frequency and improved functional status, although persistent fatigue remained. The clinical presentation was suggestive of hyperkalemic periodic paralysis, but a definitive diagnosis was limited by the patient's exceptionally late age at onset, negative genetic testing, lack of specialized exercise testing, and absence of electrophysiologic testing during an attack. This case emphasizes the importance of considering hyperkalemic periodic paralysis in the differential diagnosis of episodic weakness while simultaneously evaluating alternative neuromuscular, metabolic, hematologic, and paraneoplastic causes. Treatment response to acetazolamide and dietary modification was considered supportive of but not necessarily diagnostic of an inherited channelopathy.