A family court in the Kanto region has rejected a lawsuit filed by a plaintiff who underwent a sex-change who is seeking to have the civil registry no longer reflect female gender, the plaintiff's lawyer said.

The lawyer said Wednesday that the plaintiff has filed an appeal to a higher court.

This is the first court ruling on someone with gender identity disorder who sought a change of gender in the family registry following a sex-change operation.

According to the plaintiff's lawyer, the family court rejected the lawsuit on grounds that there are still questions on the causes of gender identity disorder.

Current law only allows changes in the civil registry on questions of gender only if a "mistake" had been made at the time of birth.

The family court ruled that gender identity disorder does not fall under that category.

The plaintiff, born a woman, underwent sex-change surgery at Saitama Medical School and has since been living as a man.

The lawyer said the plaintiff had trouble finding a job and going to a hospital because of contradictions in identification papers.

The plaintiff filed the lawsuit on grounds the Constitution guarantees the right to the "pursuit of happiness."

The plaintiff is one of six people who have undergone sex-change operations and filed lawsuits in May last year challenging the government's gender registry policy.