Refractory Hypokalemia in a Middle-Aged Woman: Unraveling the Mystery

Introduction: Severe hypokalemia is one of the life-threatening electrolyte disturbances, with a broad differential diagnosis. In cases failing standard management, rare and complex possibilities will need to be explored particularly when there is a strong family history of hypokalemia. Case Description: A 49-year-old female with Migraine history, presented with fatigue and leg cramps, found to have hypokalemia in 2 mEq range since a year and a half, despite supplementation with potassium and Lisinopril. She denied diarrhea, autoimmune history or diuretic use, stopped using Topamax and Ketorolac for the migraine, denied recent change in dietary habits. Family history revealed maternal hypokalemia. Reported having multiple joint pains. BP: 92/52, P: 91, Weight: 48.5 Kg. Potassium: 2.6 mmol/L, Chloride: 104 mmol/L, CO2:23 mmol/L, Calcium: 8.9 mg/dL, Magnesium: 2.1 mg/dL, Urine potassium: 35 mmol/L, urine pH: 5.5, Aldosterone/Renin: 0.2, AM Cortisol: 13 ug/dL, ANA: Negative, Anti-SSA and SSB Antibodies: Not detected, Anti-CCP: 86 units (Normal 0-18 units). Given the positive family history of hypokalemia, the team decided to proceed with the genetic testing which revealed a Heterozygous mutation of uncertain significance in the SLC12A3 gene. Started on KCL 40 mEq twice daily, and Lisinopril switched to Spironolactone 12.5 mg daily to be titrated as tolerated. The rheumatology considered Early Rheumatoid arthritis and started on Methotrexate 10 mg weekly. Fortunately, our patient improved with Potassium levels of an average of 3.8 mEq, improvement of the joint and muscle pain. Discussion: Our patient presented with debilitating symptoms of hypokalemia, posing significant challenges in the management, this case highlights the importance of investigating the autoimmune and genetic causes mainly in refractory hypokalemia cases, although genetically not fulfilling the criteria of Autosomal recessive disease, or classic RTA 1-Linked to patients with Rheumatoid Arthritis, It is hard to conclude the coexistence of a heterozygous SLC12A3 variant and Rheumatoid Arthritis played synergistic role or confounded one another in our patient leading to resistant hypokalemia case. Further research is needed to determine if these potential variants could contribute to potentially fatal hypokalemia.