Familial hypokalemic periodic paralysis: a case induced by concurrent hyperthyroidism.

Area of Science:

• Genetics
• Endocrinology
• Neurology

Background:

• Familial hypokalemic periodic paralysis (HypoPP) is a rare genetic disorder causing muscle weakness and low potassium.
• Hyperthyroidism co-occurring with HypoPP often suggests thyrotoxic periodic paralysis (TPP), typically in Asian males with specific gene variants.

Observation:

• A 40-year-old African American man with a family history of hyperthyroidism and hypokalemia presented with severe muscle weakness after a high-salt meal.
• Genetic testing revealed a CACNA1S gene variant, confirming familial HypoPP.
• The patient was diagnosed with both familial HypoPP and hyperthyroidism due to Graves' disease.

Findings:

• This case represents a rare instance of familial HypoPP coexisting with Graves' disease-induced hyperthyroidism, particularly in a non-Asian individual.
• The CACNA1S gene variant (c.1583 G>A, p. R528H) was identified as the cause of familial HypoPP.

Implications:

• Highlights the importance of genetic testing for HypoPP in patients with a family history, even with coexisting hyperthyroidism.
• Emphasizes the need for comprehensive genetic and clinical assessment in rare disease presentations.
• Effective management involves addressing hypokalemia, treating hyperthyroidism, and implementing lifestyle changes to prevent recurrent episodes.