Holoprosencephaly with epileptic seizures exacerbated by unpredictable hyponatremia with intermittent SIADH: A case report

Holoprosencephaly is commonly associated with central diabetes insipidus (CDI). To date, only three reports have described cases of holoprosencephaly with alternating episodes of CDI and syndrome of inappropriate antidiuretic hormone secretion (SIADH). Hyponatremia is a known risk factor for worsening seizures in patients with epilepsy, but no previous reports have described cases of holoprosencephaly with epilepsy in which seizures were exacerbated by acute-onset SIADH. A newborn girl presented with hypotelorism and polyuria and was subsequently diagnosed with semilobar holoprosencephaly and CDI. At 27 days of age, she experienced a 3-day episode of oliguria with hyponatremia, resulting in a diagnosis of SIADH. At 1 month of age, she began to have focal seizures weekly, leading to a diagnosis of epilepsy. By 6 months of age, she had experienced five episodes of SIADH, each lasting a few days and accompanied by seizure clusters. Brain MRI demonstrated hypoplasia of the third ventricle and a posterior pituitary bright spot, suggesting osmoreceptor dysfunction as the underlying mechanism for both CDI and SIADH. In patients with holoprosencephaly and CDI, particularly those showing a posterior pituitary bright spot on T1-weighted MRI, there is a risk of intermittent episodes of SIADH. Acute onset of SIADH may precipitate epileptic seizure exacerbation. In such patients, if seizures unexpectedly worsen, prompt measurement of serum sodium levels is imperative.