Pertussis pneumonia complicated by a hyponatremic seizure.

We present the case of a 6-week-old male infant who had a convulsion due to pertussis pneumonia. He was admitted to our emergency department because of lethargy and hypothermia. He developed a generalized tonic-clonic convulsion, requiring various treatments, including artificial ventilation. A chest CT showed bilateral pneumonia and laboratory data revealed hyponatremia with other features of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Although SIADH has been recognized as a cause of hyponatremia in association with pneumonia, there is little in the literature regarding SIADH caused by pertussis. Hyponatremia caused by SIADH must be considered as a differential diagnosis of seizures in pertussis infection of infants.