Sudden Tetraplegia from Hypokalaemic Periodic Paralysis Due to Cacna1s Mutation: Should Genetic Testing be Performed More Often?

Background: Paresis and paralysis are often alarming symptoms of a stroke or spinal cord injury and are typically associated with neurological disorders. However, several rare conditions, including myopathies and neuropathies, can also cause paralysis. Due to their low incidence, these diseases are often overlooked, resulting in prolonged diagnostic delays and delayed treatment. Case presentation: Here, we present the case of a 26-year-old German Caucasian male carpenter who was admitted to the neurological emergency department with acute tetraplegia. On admission, his potassium level was critically low but returned to normal levels after oral potassium supplementation. He was discharged symptom-free with a diagnosis of hypokalaemic paralysis of unclear origin. However, after he experienced a second episode approximately 1.5 years later, we performed genetic analysis and identified an R528H CACNA1S mutation as the underlying cause of hypokalaemic periodic paralysis. Further genealogical testing revealed that his asymptomatic mother and maternal grandmother were the carriers of the mutation. A decade after his initial presentation, the patient continues to manage episodes of muscle weakness effectively with oral potassium supplementation, avoiding hospitalization. Conclusion: This case highlights the importance of considering rare diseases in the differential diagnosis when common causes remain unconfirmed, emphasizing the need for timely genetic testing to facilitate an early precise diagnosis and appropriate management. LEARNING POINTS: CACNA1S mutations should be considered in patients with recurrent episodes of muscle weakness or paralysis accompanied by hypokalaemia, especially if there is a family history of similar symptoms.