The son of a missing Bronx woman was arrested Friday after he was caught using his mother’s credit card, police said.

He is being questioned about the disappearance of his mother, Joan Viau, 52, whose car was found with blood in it, a law enforcement source said.

Viau, of Carlisle Place in Williamsbridge, was last seen outside her home at about 1 p.m. on Monday. She was supposed to go to the Veterans Affairs hospital with her son, but she never returned home, police said.

She was reported missing by her boyfriend on Wednesday.

Viau is described as 5 feet, 7 inches tall, with brown eyes and salt and pepper hair. She was last seen wearing a pink shirt and black pants, police said.

Grand larceny charges were pending against the son on Friday afternoon, they said.

The investigation is ongoing, police said.