OSAKA — A 20-year-old man suffering from a mental disorder will soon file a 1 million yen damages suit against the state over the lack of a legal basis allowing mentally handicapped people to vote via mail, his family said Saturday.

Lawyers who will represent the man in Ibaraki, Osaka Prefecture, plan to argue in the lawsuit that allowing only the physically handicapped to cast postal votes conflicts with the constitutional principle of equality under law, the family said.

Early this year, the man, who suffers from anthropophobia, asked Ibaraki municipal election management authorities if he could cast his vote by mail in Osaka Prefecture’s gubernatorial election in February because of his inability to leave home.

The authorities explained that the election law permits only people with handicaps involving their legs, arms and other bodily disorders to cast postal votes.

He submitted an application to vote by mail following the government decision to hold a general election June 25, but it was rejected.

The man, who has suffered emotional difficulties since childhood, began exhibiting symptoms of anthropophobia when attending high school, forcing him to drop out, according to the family.

In 1998, Osaka Prefecture officially recognized him as having a serious mental disorder. His condition worsened about a year ago and he has been unable to leave home since then, the family said.