Huntington disease is a dominantly inherited, neurodegenerative disease characterized by choreiform movement disturbances and dementia, usually with adult onset. The rare juvenile-onset Huntington disease differs from the adult phenotype. A case presenting twice, at age 10 with all the signs of a major depression and age 14 with mutism and rigidity, is reported. Meanwhile, the father developed the adult variant of Huntington disease. The boy's diagnosis was confirmed by molecular genetic analysis and magnetic resonance imaging. It is important to be aware of hereditary conditions such as Huntington disease and to provide family counseling before genetic testing and after the diagnosis is confirmed.