Background: Semi-lobar holoprosencephalies can be seldom complicated by neurogenic hypernatremia, which must be distinguished from other causes of hypernatremia.
Case report: In two admitted children with semi-lobar holoprosencephaly, 7 months and 4 years old, biological data revealed chronic hypernatremia and hyperosmolarity without clinical signs of dehydration, which were finally attributed to a neurogenic hypernatremia.
Conclusion: Neurogenic hypernatremia must be clearly differentiated from other causes of hypernatremia since it never causes specific complications.