Hypokalemic periodic paralysis and renal tubular acidosis in a patient with hypothyroid and autoimmune disease

BACKGROUND: Hypokalemic periodic paralysis (HPP) is a rare muscle disorder characterized by episodic muscle weakness that can lead to respiratory failure. This disorder is a common manifestation of renal tubular acidosis. Renal tubular acidosis can occur associated with various systemic disorders such as Sjogren's syndrome and thyroid disorders. CASE PRESENTATION: A 58-year-old woman complained of weakness in all extremities. In the last 3 years, the patient was diagnosed with hypothyroidism and got recurrent hypokalemia without vomiting or diarrhea. The examination showed blood pressure of 110/70 mmHg, pulse rate of 98 ×/m, temperature of 36.8 °C, and respiratory rate of 20 ×/m. Motor strength 2 in all four extremities. The ECG examination showed 1st degree AV block. Laboratory examination found hypokalemia, metabolic acidosis with a normal anion gap of 13.8 meq/L, urine pH 8.0, urine anion gap 41 mmol/h. FT4 1.89 ng/dL, TSH 1.21 IU/mL. Anti TPO 20.6 IU/mL, ANA profile: strong positive SS-A (Ro), Ro-52, SS-B (La) which indicates Sjogren's syndrome. DISCUSSION: HPP is a rare case so the accuracy of diagnosis increases the success of treatment. CONCLUSION: The patient was diagnosed with HPP and renal tubular acidosis based on hypokalemia, metabolic acidosis, alkaline urine, and positive urine anion gap.