Severe respiratory syncytial virus bronchiolitis complicated by profound hyponatremia and seizures in an infant: a case report.

Background: Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis in infancy and the most frequent reason for hospitalization in the first months of life. While most infections follow a mild course, a proportion of infants develop severe disease requiring intensive care. Electrolyte disturbances, especially hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH), are a recognized complication and may trigger neurological symptoms. Severe hyponatremia with seizures is rarely documented in otherwise healthy term infants, which makes such cases clinically important. The aim of this report is to describe hyponatremia-induced seizures as a rare but clinically important complication of severe RSV bronchiolitis in a previously healthy infant. Case Description: We report a 1-month-old previously healthy female infant who presented with cough, rhinorrhea, somnolence, and progressive respiratory distress. On admission, the infant developed generalized tonic seizures, and laboratory tests revealed profound hyponatremia with serum sodium of 113 mmol/L. RSV infection was confirmed by nasopharyngeal swab. The infant required transfer to the intensive care unit (ICU), where she was intubated and mechanically ventilated. Hyponatremia was managed with 3% hypertonic saline, and she received empiric antibiotics, later tailored to ceftazidime and amikacin, along with supportive therapy. Ventilatory support was required for 7 days. Neuropediatric assessment confirmed hyponatremia-related seizures, and no underlying neurological disorder was identified. After normalization of electrolytes and gradual clinical improvement, she was discharged after 20 days in good condition. Conclusions: This report highlights that RSV bronchiolitis can, in rare cases, present with profound hyponatremia and seizures even in previously healthy infants. Routine monitoring of serum sodium at admission, cautious use of intravenous fluids, and early recognition of neurological symptoms are essential to avoid serious outcomes. Awareness of this potential complication can help clinicians initiate timely management and prevent life-threatening consequences.