Familial hypokalemic periodic paralysis: a case induced by concurrent hyperthyroidism

• Published in: BMC nephrology Vol. 25; no. 1; pp. 315 - 3
• Main Authors: Hannouneh, Zein Alabdin, Cervantes, C Elena, Sperati, C John, Hanouneh, Mohamad
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 27-09-2024; BioMed Central; BMC
• Subjects: Acetazolamide; Adult; CACNA1S; Calcium Channels, L-Type - genetics; Carbohydrates; Case studies; Causes of; Complications and side effects; Familial periodic paralysis; Family medical history; Genetic disorders; Genetic testing; Graves disease; Graves Disease - complications; Graves Disease - genetics; Humans; Hyperkalemia; Hyperthyroidism; Hyperthyroidism - complications; Hyperthyroidism - genetics; Hypokalemia; Hypokalemic periodic paralysis; Hypokalemic Periodic Paralysis - diagnosis; Hypokalemic Periodic Paralysis - etiology; Hypokalemic Periodic Paralysis - genetics; Low carbohydrate diet; Male; Musculoskeletal system; Nutrient deficiency; Paralysis; Patients; Potassium; Potassium channels (inwardly-rectifying); Rare diseases; Sodium channels; Thyroid gland; Syria; Hypokalemia; Hypokalemic periodic paralysis; CACNA1S; Graves’ disease; Hyperthyroidism
• ISSN: 1471-2369; 1471-2369
• DOI: 10.1186/s12882-024-03749-x

Familial hypokalemic periodic paralysis (HypoPP) is an uncommon genetic disorder characterized by recurrent episodes of muscle weakness and hypokalemia, typically starting in early adulthood. The existence of hyperthyroidism in the presence of HypoPP is more strongly associated with a diagnosis of thyrotoxic periodic paralysis (TPP), with most cases occurring in Asian males with pathogenic KCNJ2 or KCNJ18 variants and without a family history of the condition. This case is novel due to the combination of familial HypoPP and hyperthyroidism induced by Graves' disease, a rare occurrence especially in non-Asian populations.
A 40-year-old African American man presented with profound muscle weakness after consuming a high-salt meal. He had a significant family history of hyperthyroidism and hypokalemia. On examination, he showed profound weakness in all extremities. Laboratory tests confirmed hypokalemia and hyperthyroidism, and genetic testing identified a pathogenic variant in the CACNA1S gene (c.1583 G > A, p. R528H), with normal SCN4A, KCNJ2 and KCNJ18 sequencing. He was diagnosed with familial HypoPP and hyperthyroidism due to Graves' disease. He was started on PO methimazole 10 mg three times a day and PO acetazolamide 250 mg twice a day. He was advised to follow a low carbohydrate and low salt diet.
This case highlights the importance of considering a genetic basis for HypoPP in patients with a family history of the condition, even when hyperthyroidism is present. The combination of familial HypoPP and Graves' disease is rare and emphasizes the need for careful genetic and clinical evaluation in similar cases. Management should focus on correcting hypokalemia, treating hyperthyroidism, and lifestyle modifications to prevent recurrence.