Complete Hypokalemic Quadriparesis as a First Presentation of Sjögren Syndrome.

Abstract

Rationale:We hope to increase awareness that hypokalemic paralysis may be the first presentation of Sjögren syndrome, for which potassium-sparing diuretics can be an effective adjunct to potassium replenishment.Presenting concerns:A 73-year-old female presented to a peripheral hospital with quadriparesis and a critically low serum potassium of 1.6 mmol/L with U waves on the electrocardiogram (ECG). The initial arterial blood gas showed a pH of 7.19, bicarbonate of 13 mEq/L, and a CO2 of 35 mm Hg. Over the next 6 days, she was administered a total of 450 mEq of potassium supplements. Despite this, her potassium never increased above 2.9 mmol/L and was thus transferred to the University Hospital for further management. On arrival, her vital signs were within normal limits. Her only other symptoms were fatigue and ocular dryness. Physical exam showed slightly weakened quadriceps muscles bilaterally, graded 4/5. Examination was otherwise unremarkable. Admission investigations included a potassium of 2.8 mmol/L, chloride 118 mmol/L, sodium 136 mmol/L, and eGFR 48 mL/min/1.73 m2. Renin aldosterone ratio was normal.Diagnoses:Distal renal tubular acidosis (RTA) was diagnosed based on a normal anion gap metabolic acidosis, positive urine anion gap, and elevated urine potassium to creatinine ratio. Investigation of underlying causes revealed a positive Antinuclear antibody (ANA), elevated rheumatoid factor, and high anti-Ro/SSA titre which directed us toward a unifying diagnosis of Sjögren syndrome. A renal biopsy was undertaken as an outpatient and demonstrated severe interstitial nephritis with acute and chronic components, parenchymal scarring, atrophy, and small vessel arteriosclerosis.Interventions:In the acute setting, the patient was treated with bicarbonate and amiloride in addition to potassium supplementation.Outcomes:The patient’s hypokalemic paralysis and metabolic acidosis were corrected.Lessons Learned:Severe hypokalemic paralysis in distal RTA associated with Sjögren syndrome can be successfully treated with amiloride in addition to potassium supplementation. We also review the literature on the aberrancies seen in H+ATPase, Band 3, Pendrin, and carbonic anhydrase that may underlie the pathogenesis of distal RTA in Sjögren syndrome.