Refractory hyponatremia in neuromyelitis optica in a pediatric patient: A case report

RATIONALE: Neuromyelitis optica spectrum disorders (NMOSD) is a rare autoimmune disease predominantly involving optic nerves and spinal cord, and possible comorbidities including syndrome of inappropriate antidiuretic hormone secretion or urinary complication. We reported a young girl diagnosed with NMOSD presented with refractory hyponatremia, acute urine retention, and general weakness. Clinical symptoms improved gradually after receiving intravenous immunoglobulin, high-dose methylprednisolone, and plasmapheresis. NMOSD should be kept in mind in adolescence with acute urine retention, intermittent fever, and hyponatremia. PATIENT CONCERNS: A 15-year-old girl admitted to our hospital due to no urination for 2 days. DIAGNOSIS: Aquaporin-4 antibodies were detected showing positive both in serum and cerebrospinal fluid. Long transverse myelitis in cervical and thoracic spinal cord and optic neuritis was revealed in magnetic resonance imaging. INTERVENTIONS: Intravenous immunoglobulin 2 g/kg was infused totally in 4 days, and methylprednisolone pulse therapy was subsequently followed in 5 days; followed by 5 courses of plasmapheresis a week later. OUTCOMES: Her muscle power, syndrome of inappropriate antidiuretic hormone secretion condition, and urinary function were all improved after immune-modulated treatment course; NMOSD relapsed twice within the first year after diagnosis, however no relapse of NMOSD in the subsequent 1 year. LESSONS: To the best of our knowledge, this was the first childhood case of NMO accompanied by refractory hyponatremia in the reported literature. In childhood cases presenting with refractory hyponatremia and limb weakness, NMO or NMOSD should be considered possible diagnoses despite their rarity in pediatric cases.