TikToker Taylor Rousseau Grigg died aged just 25 from complications of Addison’s disease and asthma, her family told Today.com. Rousseau Grigg’s death last week was “sudden and unexpected,” her husband Cameron Grigg said in an Oct. 5 Instagram post.

The young TikToker became known for posts about her life. She shared that she had received a diagnosis in an Aug. 8 “health update,” but did not provide any information about her condition. Experts say Addison’s disease is rare but can quickly become life-threatening if not treated properly.

Here’s what you should know about the disease.

What is Addison’s disease?

Addison’s disease is an autoimmune disease that affects about one in 100,000 people and in which the body attacks its organs, particularly the adrenal glands. It is also called primary adrenal insufficiency because the condition causes a person’s adrenal glands to produce too few of two important hormones. “The most important thing is the hormone cortisol – you can’t survive without cortisol,” says Dr. Anne Cappola, an endocrinologist at Penn Medicine, told Yahoo Life.

Cortisol is often referred to as the “stress hormone,” and its levels rise as part of the “fight-or-flight” response when we are in real danger or otherwise distressed. But it plays a vital role in our body. “Cortisol is an important hormone for blood pressure. “So if you don’t have enough of it, you can go into an adrenal crisis and die,” explains Cappola. But, she adds, the body has a lot of “redundancy” when it comes to cortisol. We have two adrenal glands – and other cells too – that produce cortisol, and in most cases we could get by with the amount of the hormone produced by one. For this reason, symptoms of Addison’s disease may appear slowly over time.

What are the symptoms?

Addison’s disease manifests itself with a “constellation” of symptoms, says Dr. Theodore Friedman, endocrinologist and chief of internal medicine at Charles R. Drew University, told Yahoo Life. These include fatigue, weight loss, nausea, diarrhea, stomach pain, joint or muscle pain, dehydration, low blood sugar, and cravings for salty foods. There may also be hyperpigmentation, or darkening of the skin, which can cause people to appear tanned.

Rousseau Griggs said in her August health update that at times she “lay in bed in pain” and felt too weak to carry a suitcase or walk to the mailbox. She added that she had only found out what she was suffering from a few months ago and that she had been “struggling the whole time and felt like I was dying.”

While symptoms tend to develop slowly over time, in some cases they can worsen quickly, says Friedman. “You can be healthy one day and sick the next day,” he explains. “It can happen very quickly.” According to the Cleveland Clinic, most people are diagnosed between the ages of 20 and 50 as the chronic effects of the disease accumulate.

Addison’s disease can be treated with steroids

Cappola and Friedman tell Yahoo Life that people with Addison’s disease usually need to take one or two medications to replace the hormones their bodies don’t produce enough: hydrocortisone, a steroid that supplements cortisol, and fludrocortisone, a second hormone called aldosterone. The latter helps keep the body’s water and salt levels balanced, says the Cleveland Clinic, so people with Addison’s disease may need to consume more sodium when they exercise.

By taking these steroids properly — hydrocortisone sometimes needs to be taken in varying doses, between two and four times a day, Friedman says — a patient with Addison’s disease can live a relatively normal life.

How Addison’s illness can be fatal

The disease must be treated carefully. The body needs cortisol at all times, “but you especially need cortisol during times of physical stress,” explains Cappola. The body’s cortisol needs can fluctuate drastically throughout the day and “increase sharply during times of stress, such as during an infection.”

This is particularly dangerous when a patient’s body is trying to fight off a cold or other illness. “An infection causes you to chew through (your steroids) and then be unable to fight the infection,” Friedman explains. People with Addison’s disease need an extra dose of cortisol, often in injection form, during these times because their body cannot produce enough to meet the needs on its own.

The biggest concern, however, is that the drop in cortisol triggers an adrenal crisis, and if there isn’t enough hormone, “most importantly, you would see blood pressure start to drop, and if your blood pressure isn’t like that.” “If the If the value is not high enough for a long time, you can die from it,” says Cappola.

Although it’s not clear what exactly happened to Rousseau Grigg, both experts say a combination of an adrenal crisis from Addison’s disease and asthma could be fatal. “It might not be the asthma attack itself,” says Cappola. “But she may have had some sort of upper respiratory infection that triggered an asthma attack and an adrenal crisis. You can die from both.”

Cappola suggests that the rediagnosis may mean that Rousseau Griggs was less prepared to understand what was happening and how to deal with it. She adds that the drop in blood pressure during an adrenal crisis may have impaired judgment and made it more difficult to get timely help or further medication.

Both experts say Addison’s is a rare diagnosis that most people probably don’t need to worry about unless a patient has had persistent symptoms (which would warrant a doctor’s visit). “What should reassure you is that the body has many built-in duplicates of adrenal tissue that produce these hormones,” says Cappola. “It really takes a chronic destructive process to get to the point where someone develops these symptoms.”

While corticosteroids such as hydrocortisone and prednisone are helpful for people with Addison’s disease, Cappola cautions people not to take the medications without a doctor’s recommendation. “Be careful when taking corticosteroids such as hydrocortisone or prednisone,” warns Cappola. “There are people out there who think they have adrenal fatigue and are taking these (as) supplements, and they shouldn’t; You don’t want to mess with those adrenal glands.” Because if you take steroids for a long time and then abruptly stop, your body can go into an adrenal crisis, even if you don’t have Addison’s disease.