Abstract
A 16-year-old Japanese girl presented to the emergency department with a complaint of increased muscle pain in the thighs and difficulty walking. Laboratory examinations revealed elevated levels of creatine phosphokinase, severe hypokalemia (1.4 mmol/L), hyperchloremic metabolic acidosis with a normal anion gap, and a urinary pH of 7.5. The patient was thus diagnosed with hypokalemic rhabdomyolysis due to distal renal tubular acidosis. Furthermore, the patient was diagnosed with Sjögren syndrome based on a high titer of anti-SS-A antibodies, reduced tear production on the Schirmer test, decreased salivary secretion on the Saxon test, and labial salivary gland pathology. Although her muscle symptoms resolved rapidly with fluid and potassium replacement therapy, hypophosphatemia and hypouricemia persisted. The patient was subsequently diagnosed with Fanconi syndrome based on elevated urinary β(2)-microglobulin and pan-aminoaciduria. Following induction therapy with prednisolone, mycophenolate mofetil was added for maintenance based on renal pathology, which successfully reduced the urinary β(2)-microglobulin levels. This report describes a case of hypokalemic rhabdomyolysis due to concurrent distal and proximal renal tubular dysfunction in a patient with juvenile Sjögren syndrome. Early detection of renal tubular dysfunction is crucial to prevent life-threatening complications, such as rhabdomyolysis.