Primary Sjögren syndrome is a chronic autoimmune disorder that primarily affects the exocrine glands and may present with extraglandular manifestations, including renal tubular acidosis (RTA). We report the case of a 28-year-old postpartum female who presented with rapidly progressive limb weakness and severe hypokalemia; she was ultimately diagnosed with RTA as the initial manifestation of primary Sjögren syndrome. During treatment with intravenous sodium bicarbonate, the patient developed acute hypernatremia, which was subsequently complicated by central pontine myelinolysis (CPM). This iatrogenic neurological event highlights the potential risks associated with rapid correction of metabolic acidosis in autoimmune conditions. The patient was treated with corticosteroids, rituximab, and intravenous immunoglobulin, resulting in marked clinical and radiological improvement. This case underscores the need for caution when rebalancing electrolytes in patients with autoimmune-mediated RTA and contributes to the limited literature on CPM in this context. Early recognition and appropriate immunosuppressive therapy may play a role in optimizing neurological recovery.