The actress revealed that beginning in February, she underwent three surgeries - which she succeeded in keeping secret from the public - in which her breasts were removed, and later replaced by implants.
"I wanted to write this to tell other women that the decision to have a mastectomy was not easy. But it is one I am very happy that I made," Jolie wrote.
"My chances of developing breast cancer have dropped from 87 per cent to under 5 per cent. I can tell my children that they don't need to fear they will lose me to breast cancer."
The actress also hinted that she might, at some point, have her ovaries removed, saying that she had "started with the breasts" because her risk of breast cancer was higher than that for ovarian cancer. She did not say how long ago she was diagnosed with the faulty gene.
While admiring Jolie's straightforwardness, cancer surgeons and others in the medical community were quick to point out that hereditary cases of breast cancer account for only about 5 per cent to 7 per cent of all cases diagnosed each year. And those connected to the BRCA1 and BRCA2 genes are an even smaller group.
And so, women shouldn't just run off and get tested for those genes, said Dr Robert Shenk, medical director of the Breast Center at the University Hospitals Case Medical Center in Cleveland.
"My worry is that people will be inappropriately tested," said Dr Shenk.
"Awareness is great, but people shouldn't just run in off the street and get a test."
Instead, he said, genetic counseling, including a close review of a patient's family history, is crucial.
Nagy, the genetic counselor, who is also president of the National Society of Genetic Counselors, agreed.
"The clues are in the family history. Has there been cancer in multiple generations?" she said. "Are there clusters of cancers, like breast and ovarian, on the same side of the family? Has the cancer been diagnosed at an early age - under 50?"
If those factors exist, Nagy said, she conducts a thorough risk assessment with the patient. And if testing is warranted, there still needs to be some thought beforehand as to what one might do with the information.
"It might not necessarily be surgery," Nagy said. "It might be much more frequent screenings. Surgery isn't right for everyone."
That's the decision that Gabrielle Brett made - at least initially. Brett was only 23 when she tested positive for the BRCA1 gene. She had just met her future husband, James, a month earlier. She wanted to have a family, so she waited.
But at age 29, her husband said she shouldn't wait any longer. She should have her breasts removed before they had kids, even though she wouldn't be able to nurse them. She ultimately agreed. She had the surgery and then had two children. Now 35, she is two weeks from her due date with her third.
Brett woke up in the middle of the night, read about Jolie's article on Facebook, and excitedly woke her husband. "It's amazing to hear that someone so famous went through the same thing," she said in a telephone interview. "It makes me realise we are all on the same journey."
Brett also figures that Jolie went through some tough moments, however serene she sounded in her article.
"I'm sure it wasn't quite so simple," she said. "There's sadness, anger, fear. I did a lot of crying alone in the car. But once I had the surgery, I felt a huge weight come off of me. I was no longer worrying whether there was cancer growing inside me somewhere. I felt nothing but relief."
And, she said, it was crucial that she was accompanied throughout her journey by "my own Brad Pitt" - her husband, who was there through every moment, as Jolie says partner Pitt was for her at the Pink Lotus Breast Center in southern California.
There is one part of the journey Brett has not tackled yet: removal of her ovaries. That, she said, will come a bit later, when she is 40.
Doctors stress that no one solution is right for everyone who tests positive. And even for those with a risky family history, it's not necessarily always right to test right away, they say.
"You don't necessarily want to test an 18-year-old, sending her into a panic at such a young age," said Dr Shenk. "You might consider that she's unlikely to get cancer in her 20s. You would maybe test her later."
Another potential downside to the testing: the cost, which can reach US$3,000, though it's usually covered by insurance and there are programmes for women who can't afford it.
And some women might simply not be prepared for the results, said Dr Eric Winer, head of the breast program at the Dana-Farber Cancer Institute in Boston.
"Once you get the information, you have to be able to deal with it," he said.
If one does test positive, Dr Winer stressed, it could be a reasonable solution to undergo intensive surveillance with MRI tests and mammograms. Or, some women choose to remove only their ovaries, which in pre-menopausal women seems to reduce the risk of breast cancer, too.
But in Jolie's case, Dr Winer said, it's hard to argue with her choice of preventive surgery. "I tend to be a less-is-more doctor," said Dr Winer. "But I do think the choice she made is a rational, reasonable one."
There is a risk, he noted, that with the actress's celebrity power, people will see her choice and think it's the only one. If they do get cancer, "most women are well-served by conservative surgery, as in a lumpectomy," with chemotherapy and/or radiation, he said.
But any risk is outweighed by Jolie's ability to promote awareness, Dr Winer added.
"The more people who ask their doctors about this, the better."
Dr Kristi Funk, founder of the Pink Lotus Center where Jolie was treated, agreed.
"We hope that the awareness she is raising around the world will save countless lives," Dr Funk said.
Jolie's most positive influence, some say, may be in the fact that such a glamorous woman has come forward - in great detail - to talk about how one can lose one's breasts and still remain, well, a woman.
"I do not feel any less of a woman," Jolie wrote in her article. "I feel empowered that I made a strong choice that in no way diminishes my femininity."
