Citing health concerns, freshman Rep. Frank Ballance (D-N.C.) abruptly changed course and announced Friday he will not seek a second term in November. He had filed to run earlier this week.

In a statement, Ballance said he had been diagnosed with myasthenia gravis, a neuromuscular disease, in early February. He said he began to reconsider his re-election plans after suffering a setback on Wednesday that required him to seek treatment at National Naval Medical Center, in Bethesda, Md.

“Considering the number of candidates in the primary and those expressing an intent to file, I do not believe that the current state of my health will allow me to mount the vigorous campaign necessary to win,” Ballance said.

Ballance’s first term in office has been shadowed by an ethical cloud.

A federal grand jury is probing a nonprofit substance-abuse prevention program run by a foundation Ballance founded and once chaired.

A state audit released in October 2003 revealed that the foundation had numerous conflicts of interest and had made $325,000 in questionable payments. Ballance helped steer money to the foundation when he served in the state Legislature.

According to state officials, the FBI also has been looking into the foundation’s dealings.

Ballance, who filed to run for re-election on Tuesday, won 64 percent of the vote in 2002, in a race that was not vigorously contested by Republicans.

As of mid-day Friday, when the state’s candidate filing closed, four Democrats and two Republicans filed to run in the northeastern 1st district.