A 44-year-old man filed a lawsuit Monday alleging that he was molested as a young patient by a junior doctor at Tufts Medical Center.

The man, whose identity is shielded in court documents, was admitted to Tufts in 1983 — known then as New England Medical Center — when he was 11 years old. He was treated in a pediatric unit for an eating disorder for four months, and then went to an outpatient clinic for follow-up care.

He said Dr. William Richard Bonner befriended him during his hospital stay and then molested him during several unchaperoned exams at the clinic.

Bonner was a resident ­— a doctor in training — at the time, according to the lawsuit. He went on to continue his training in Atlanta and is now a pediatric anesthesiologist at Children’s Healthcare of Atlanta, according to his physician profile on the Georgia medical board website.

Neither Bonner nor his attorney returned telephone calls from the Globe.

Tufts Medical Center, which was also named in the lawsuit filed in Suffolk Superior Court, said in a written statement it “takes any allegation such as this seriously.’’ The hospital said “the allegations were not substantiated’’ in an investigation conducted in 1984. It would not provide details of the inquiry or say whether hospital officials reported the complaint to outside authorities.

During an interview with the Globe, the former patient and his mother said Bonner gave him gifts during his hospital stay, including athletic jerseys and sports equipment, and often called him at home after he was discharged.

At the time, Bonner’s alleged attentiveness did not seem improper to the former patient, but “when I look back at it as an adult, it seems highly unusual that a doctor would allow that much attention on a young boy,’’ the former patient said.

The Globe does not identify alleged victims of sexual assault without their permission, and is not identifying the patient’s mother in order to protect his identity.

The boy saw Bonner in the outpatient clinic until one day when the former patient refused to go into the exam room. His mother was surprised and when she asked him why, her son said Bonner required him to remove all his clothes and said the exam was painful. The former patient told the Globe he had been “frozen with fear’’ as Bonner had fondled his genitals on the exam table.

The mother said she confronted Bonner, who asked them to leave.

She said she later told another member of her son’s medical team, who talked to her son about what happened during the exam. This doctor said she believed the boy and would ask someone from the hospital to call the family, according to the mother.

A hospital mediator then came to their home on a Saturday, the mother and son said. He asked how the family wanted to handle the situation, but advised them that if they went to outside authorities, the boy would probably have to testify in court.

The mother said she decided not to go that route because she was worried it would be too difficult for her son.

“My 100 percent attention was on getting my son well,’’ she said.

The former patient, who lives in the Northeast but no longer in Massachusetts, said he decided to file a lawsuit now because he has three children, ages 12, 10, and 5.

“As they were getting older, they would routinely go through annual checkups and appointments and that became a trigger for me,’’ he said. “It triggered something inside me to take action. I also wanted to make sure no one else would have to go through what I did.’’

►Phillips Academy inquiry finds five cases of abuse. B3

Liz Kowalczyk can be reached at kowalczyk@globe.com.