Type 1 Diabetes Mellitus and Familial Hypokalemic Periodic Paralysis: A Management Dilemma

Background: Familial hypokalemic periodic paralysis (FHPP) is a rare condition characterized by episodes of painless muscle weakness associated with hypokalemia. It can be precipitated by heavy exercise and high carbohydrate meals. There have been cases illustrating treatment options to decrease the frequency of episodic weakness. However, insulin use in patients with FHPP has not been well studied or documented in literature. Clinical Case: A 21-year-old male with known FHPP (heterozygous positive CACNA1S R1239H mutation) presented with nausea, vomiting, abdominal pain, and profound weakness. He had 1/5 strength in his upper and lower extremities bilaterally on examination. He was found to be in diabetic ketoacidosis (DKA). Insulin drip was initiated per DKA protocol and eventually converted to subcutaneous insulin. He continued to be weak and persistently hypokalemic, requiring potassium replacement (200 mEq/day). He had been on acetazolamide as preventive treatment for FHPP. It was switched to spironolactone in efforts to better control his potassium levels. His strength improved gradually, and he recovered 5/5 strength in his upper and lower extremities bilaterally by day 3 of admission. His weakness did not acutely worsen after receiving subcutaneous insulin. Further testing revealed elevated glutamic acid decarboxylase (GAD) antibodies consistent with type 1 diabetes mellitus (T1DM). His serum potassium on discharge was 4.4 mEq/L. He was discharged with subcutaneous insulin, potassium chloride 40 mEq three times daily, and spironolactone 100 mg daily. After discharge, serum potassium levels remained stable and potassium requirement decreased significantly to 40 mEq once daily. Conclusion: This case illustrates the management dilemma between an unusual combination of diseases. The balance of potassium levels between insulin use in T1DM and FHPP creates significant challenges. Fortunately, the use of subcutaneous insulin in this patient did not appear to trigger episodic weakness. Further studies of hypokalemic periodic paralysis are critical to the institution of appropriate therapy and prevention of symptoms in patients with these conditions. Careful replacement and monitoring of potassium is recommended as patients require high doses of potassium during acute episodes of flaccid paralysis, and requirement significantly decreases after an acute episode.