Esther Choo, an emergency room doctor in Portland, Ore., had all the right credentials.

A medical degree from Yale University. A master’s degree from Oregon Health & Science University. A residency at Boston Medical Center. Multiple awards and dozens of published research manuscripts. Not to mention 15 years of experience practicing medicine.

But, according to Choo, none of that mattered to some of her patients who had one problem with her. She’s Asian.

Choo shared her experience in a long thread on Twitter in the aftermath of the violence in Charlottesville last week. Her tweets have since been retweeted hundreds of thousands of times.

During encounters with racist patients, Choo said she usually tries to reassure them that they’re in good hands, that she trained at elite institutions, and that she’s the most qualified person to treat them. But they often either leave or choose to be cared for by interns, as long as they’re white.

“Breathtaking, isn’t it? To be so wedded in your theory of white superiority, that you will bet your life on it, even in the face of clear evidence to the contrary?” Choo tweeted. “Sometimes I just look at them, my kin in 99.9% of our genetic code, and fail to believe they don’t see our shared humanity.”

She said a few become uncomfortable with their own remarks and apologize.

“You see, it’s a hell of a hard thing to maintain that level of hate face-to-face,” Choo said.

Choo’s experience with racism is not new and certainly not exclusive to the United States.

A 2011 survey of 377 family medicine graduates from two Canadian universities found that 35 percent of them experienced some form of discrimination from patients. About 27 percent of respondents said they were discriminated against based on their gender, while 16 percent said patients were hostile to them because of their race.

In June, a video captured a woman as she stormed through a Canadian medical facility, adamant that she wanted a white doctor — not a brown one and not one with an accent.

“So you’re telling me that my kid has chest pains, he’s going to have to sit here until 4 o’clock?” she told an employee at a walk-in clinic in Mississauga, Ontario. “Can I see a doctor that’s white, that doesn’t have brown teeth, that speaks English?”

One person was killed and 19 were injured amid protests of a white nationalist rally in Charlottesville on Aug. 12. Here’s how the city became the scene of violence. (Elyse Samuels, Zoeann Murphy/The Washington Post)

Tamika Cross, an obstetrician and gynecologist, said last year that she was on a flight from Detroit to Minneapolis when a fellow passenger suddenly became unresponsive. She flagged down a flight attendant and offered to treat the man.

The response to her, according to Cross: “Oh no, sweetie, put your hand down. We are looking for actual physicians or nurses or some type of medical personnel, we don’t have time to talk to you.”

Cross said she was shut down because she was black.

A 2000 study published in the Journal of the National Medical Association found that racism, doubt in their capabilities and a strong desire to prove themselves in the medical field are the main sources of stress among black physicians. Researchers interviewed 10 doctors in Ohio, all of whom described a long history of racism and discrimination they experienced from fellow doctors, patients, office staff and members of the community.

One research participant described skin color as “the badge you wear,” and said people “make their initial assessment based on that.”

Another participant said:

There’s always a ‘but,’ that you always feel that people are looking at you as well, a nonminority person could have done just as good if not better than you. Or, the reason you’re doing as well as you’re doing is because somebody is trying to hold you up as being an example, like ‘Here’s our token minority that we have.’ So, they pull you out of the closet and say, ‘We’ve got a minority, too’ … It’s like ‘This is our boy, he’s so good.’

Others said their experiences strengthened their self-confidence and self-esteem.

“The way I see it now is, I can get around everything. If everything collapsed around me now, I would still survive … That if me and the white guy both got here, maybe I’m a little better than he is to have made it,” one participant said.

John Henning Schumann, a Jewish doctor, said he’s had encounters with patients that sometimes result in awkward conversations.

“I’ve been asked point-blank by patients if I’m Jewish,” Schumann wrote last week in a column published by NPR. “Being asked such a question is unnerving since it bears no resemblance on my abilities as a doctor.”

Sometimes, after saying that he is Jewish, patients surprise him with their response: “Good. I always like Jewish doctors, because they’re the smart ones.”

Schumann said that “positive prejudice” is better than the alternative, and he often takes the compliment.

“But doubt lingers in me about the origins of such a sentiment,” he added. “The idea is ironic, too, because for much of the 20th century, Jews were limited in American medicine because of strict medical school quotas.”

Choo was not immediately available for an interview Monday morning, but she said earlier that her thread generated responses from other medical professionals who said they have had similar experiences.

“Some said they felt powerless to even mention that they experience racism from patients or staff members,” Choo said in a statement published by the Oregon Health & Science University, where she also works as an associate professor. “Some felt that their performance evaluations or positions might be at risk if they spoke up.”

Choo said the violence in Charlottesville has empowered many to speak up, but she added that medical professionals who witness bigotry against their colleagues should not be timid or oblivious. Health institutions must also establish clear, visible policies against discrimination, Choo said.

Although the “land mines of gender and color” did not obstruct her path to becoming a doctor, Choo said they still affect her professional life every day. Now, midway through her career, she’s learned to deal with racism with calmness.

“I used to cycle through disbelief, shame, anger. Now I just show compassion and move on,” she said in one of her tweets. “I figure the best thing I can do is make sure their hate finds no purchase here.”

Here's why you can't ignore violent right-wing extremists when it comes to domestic terrorist attacks. (Monica Akhtar/The Washington Post)

Cleve R. Wootson and Derek Hawkins contributed to this story.