(CNN) Sometimes, you don't know the exact moment when your life has changed.

For Monica Schulman, 38, one of the first signs that her health -- her life -- had changed was so slight that it only began to bother her because it kept happening.

"I was standing in the bathroom, and I kept noticing while I was brushing my teeth that my left side toes kept kind of curling under, and they were getting tense all of a sudden. And I really didn't think anything of it for months, but I kept doing this," said Schulman, of Atlanta, a part-time teacher and a mother of four. "And I was thinking: This is so weird. I don't know why I keep curling my toes under."

Though it was unusual enough to make her pause, she did not go see a doctor. Schulman took that important step only after noticing another symptom.

Monica Schulman, a mother of four, was diagnosed with Parkinson's Disease when she was 37.

"I was visiting my sister in New York, who at the time was going through chemo because she got diagnosed with breast cancer, and we would be walking a little bit through Manhattan," Schulman said. "And I kept telling her, 'My left arm is just not swaying!' "

She'd never thought about arm movements, but once she experienced it, she knew that something was off: "My arm was just kind of tight, and it was just laying there."

She also felt the barest shiver of a tremor that was unnoticeable to other people. She'd gone to the doctor some time ago about a tingling sensation, and he had run some tests -- "I think he was trying to see if I had (multiple sclerosis)" -- but he'd found nothing wrong. "You're fine, you're fine," he told her.

After her trip to New York, she turned to Google before consulting a physician.

"I pretty much diagnosed myself," Schulman said. "I typed my symptoms in, and everything that popped up that I read was Parkinson's-related."

A neurological disorder, Parkinson's disease can bring tremor, stiffness, slowness of movement, trouble balancing, problems walking and difficulty coordinating movement. These are the obvious symptoms and the reason why Parkinson's is sometimes referred to as a "movement disorder." Yet other symptoms are also common: Patients can experience depression, sleep problems, anxiety, fatigue and constipation.

After her Google search, Schulman turned to her family: "And everybody was like, 'You do not have Parkinson's. You're too young.' "

Most Parkinson's patients are diagnosed around age 58.

"They're like, 'You're crazy,' " said Schulman. "And I was like, 'I really think I do.' "

After more research, she asked her husband, Jeremy, to help her get in to see In the face of disbelief, Schulman knew that she needed to find the best doctor to validate her self-diagnosis.After more research, she asked her husband, Jeremy, to help her get in to see Dr. Stewart Factor , a neurologist and director of the Movement Disorders Program at the Emory University School of Medicine in Atlanta. He is an expert in the field, and his appointment calendar is booked many months in advance.

Her husband told office staff members, "she's really young; she's freaking out," and eventually they took pity and found a time for Schulman to see the doctor sooner rather than later.

In a waiting room filled with elderly people, Schulman gloomily observed the same symptoms she was experiencing: the rigidity, the tremors. Her name was called.

"The first time Dr. Factor saw me, he was like, 'Wow, you're young,' " she said. Immediately, he explained that there's no "100% test" to tell somebody they have Parkinson's disease.

Still, the news was grim. After a symptom check and neurological evaluation, he said he believed that Schulman had Parkinson's.

"I was OK, but pretty hysterical," Schulman said.

The cause of Parkinson's

People under the age of 40 make up about 15% of all Parkinson's cases, according to Factor.

"We call that young-onset Parkinson's, while under the age of 20 is juvenile-onset of Parkinson's disease," Factor said. "That's much less common. The youngest person I've personally seen with Parkinson's had onset at age 18."

Why some patients develop Parkinson's at a very early age is not completely clear, explains Dr. Rebecca Gilbert, an associate professor of neurology at NYU Langone Medical Center. "But it does seem that patients who get it early tend to have a more prominent genetic component," added Gilbert, who is also a movement disorder specialist.

Monica Schulman with her husband, Jeremy, recently enjoying a night out together.

Schulman's genetic tests revealed a mutated LRRK2, one of the most prominent and researched Parkinson's disease genes.

According to Factor, between 1% and 3% of all people with Parkinson's disease in the United States have this mutation. It's more common among some ethnicities, such as Ashkenazi Jews and North African Berbers.

Yet LRRK2 has only about a 30% "penetrance," Gilbert said: "If you inherit the abnormal gene, you have a 30% chance of developing Parkinson's."

Gilbert acknowledges that the genetics are "very complicated and getting more complicated every day." Oftentimes, she says, patients who develop the disorder at an older age have some genetic component.

In fact, a whole variety of genes either cause or are associated with or contribute to the risk of developing Parkinson's disease.

"There are well over 20 genes that impact Parkinson's," Factor said. "There are five of them that are what we call causative -- in other words, the mutation causes the disease -- whereas the other genes just impact risk."

As he explains, the risk genes are teaching scientists about what systems (and symptoms) might be involved in Parkinson's. For instance, one risk gene regulates immune response, and it is well-known that inflammation in the brain is a symptom of the condition.

"Some have thought that the progressive nature of the disease may be because of this ongoing inflammatory change in the brain," Factor said.

Head Trauma

Schulman, who has spent a good deal of time researching her illness, knows that a possible contributing factor -- or in some cases a cause -- is head trauma. (Sports legend Muhammad Ali's doctors believe that boxing-related brain injuries led to his Parkinson's diagnosis.)

"There are some studies that have shown having a history of head trauma with loss of consciousness at some early time in your life can be associated with the development of Parkinson's later, but the impact it has on your risk is small," Factor said. "Muhammad Ali was a complex case."

Ali had young-onset Parkinson's diagnosed in his late 30s, Factor explains. Early in the course of his disease, some doctors said Ali looked like he had typical Parkinson's disease, with a tremor in one hand, but over time, his symptoms became compounded by effects from the trauma of his career.

"People who were boxers that get pugilistic Parkinson's often don't respond to medications, and they have a different look," Factor said.

"When I was 18 years old, I was in a really bad car accident in 1996 where I flipped my car seven times," Schulman said. "I broke high vertebra in my neck and had to wear a halo." She also began suffering from from anxiety and depression.

Today, she wonders "if that impact is why what's happening now is happening."

Dopamine in the brain

At their first meeting, Factor recommended that Schulman get a DaTscan, a nuclear imaging test that looks at brain chemistry, specifically the integrity of dopamine cells.

If you have normal integrity of dopamine cells, you don't have Parkinson's, Factor explains, but if the test results are abnormal, "then you can have any one of these series of diseases that results in the death of dopamine cells, Parkinson's being the most common."

The scan showed "that I already had some dopamine loss on one side of the brain, on the right side, so that affects the left, and that's where my symptoms are," Schulman said.

Despite the results, Schulman says, she "wasn't really convinced" and asked for recommendations for second opinions. Two other doctors reached the same diagnosis after they learned her symptoms and saw the DaTscan results.

"So why do you have a lack of dopamine in your brain? You have a lack of dopamine in your brain because a certain cell that produces dopamine dies. There's degeneration of a specific type of neurons," Gilbert said.

Though it's "more complicated than that" because the dopamine deficiency mainly accounts for motor symptoms of the disease, Parkinson's "affects a lot of different areas of functioning," including autonomic functions (such as blood pressure and breathing), cognition and urination.

Treating Parkinson's, then, is a matter of producing dopamine in the brain.

Medication

A key of Parkinson's treatment is the drug levodopa , which is converted into dopamine in the brain and is "the cornerstone" of Parkinson's therapy, says Factor. Accordingly, he has prescribed it for Schulman along with a second drug, rotigotine.

Parkinson's patients experience "ons and offs," said Factor: motor fluctuations in response to the drug. These fluctuations appear as involuntary movements, known as dyskinesia. Actor and Parkinson's patient Michael J. Fox has this symptom and writes in his autobiography about overmedicating with levodopa early in his diagnosis to "cover" his symptoms and keep working.

Some researchers believe dyskinesia is caused by medication flowing in waves or pulses in the brain. Some believe that taking too much levodopa causes dyskinesia.

One of the big discussions in the field is whether and when to start treatment with levodopa, Factor explained, since the drug contributes to dyskinesia. But it is not the only cause.

"I personally believe that the progressive nature of each individual's disease predestines them to get it at some point," Factor said. "So if you delay the levodopa to try and prevent it, you're not going to prevent it, and you're going to lose a period of time when patients can have a really good response."

He tends to use it early, to give young patients the best opportunity to continue working. To limit the dose and delay fluctuations, he adds a second drug to the regimen.

Another reason for giving levodopa to young-onset patients is that they can undergo deep brain stimulation surgery once the fluctuations become troublesome.

"Young people are the best candidates, because they are healthy and will have long-term benefits from the surgery," Factor said.

As Gilbert explains, delivery of medication is one of the most important areas of Parkinson's research right now. The goal is finding a way to deliver medication that stimulates the production of dopamine within the brain in a more continuous, sustained way. Among the new delivery systems, pharmaceutical researchers have developed infusion systems to pump medication directly into the small intestines.

One new class of drugs under development is chemically similar to caffeine, says Factor, because caffeine appears to lower the risk of getting Parkinson's disease in people with certain genes. Surprisingly, nicotine and other environmental toxicants may have a similar effect, lowering the risk for people with a certain genetic profile.

"We very rarely see Parkinson's disease in active smokers," Factor said.

From Schulman's perspective, all the research focused on medication is somewhat disappointing.

"It's all symptom management," she said, adding that she doesn't expect a cure in her lifetime. Despite recent advances in neuroscience, a cure for this complex disease is not on the horizon.

At the same time, even though she knows "there's no reason to suffer and it's not necessarily going to get worse if you begin to take levodopa right now," she still has some worry about taking too much levodopa.

"The tremor is annoying when I'm out at a restaurant with friends and my meds are wearing off," Schulman said. "I can feel myself moving, so I try to sit on my hand.

"It's also hard taking all these meds regularly. It's like three times a day," she said. "But I'm dealing with it and functioning."

Prognosis

"Everyone who is born holds dual citizenship, in the kingdom of the well and in the kingdom of the sick," Susan Sontag wrote in her book " Illness as Metaphor ," adding that sooner or later, each of us will count ourselves among the citizens in the country of sickness.

But not everyone in the kingdom of the sick believes the stamp on her passport.

"There's still part of me that doesn't believe that I have Parkinson's," Schulman admitted. "I just have that percentage that still thinks they all got it wrong and maybe it's something else.

"I'm trying to get over this denial phase, because I think I've been in it a little too long."

In January, she will leave her job as a preschool teacher and start focusing on "going to the gym every day and getting a trainer and start moving more and taking it a little more seriously."

Exercise is the best thing Parkinson's patients can do for themselves, according to Gilbert, who says, "lots and lots of things are improved when patients exercise." Many studies have showed that exercise improves symptoms of depression, helps with cognition and slows the progression of motor symptoms.

Although Factor refers to her symptoms as mild, Schulman says, "to me, it's pretty not mild, because I feel them." She noticed that her tremor has worsened since her diagnosis in early 2015 and asked Factor if that meant she is progressing quickly.

"It's slow and slower, that's what he said: People progress slow or slower," Schulman said. "They don't know how much I'll progress. They don't know if I'll stay this way and never get worse. They know to a point you do get worse, but everybody's different. Two years from now, I could be a lot worse or be where I'm at right now."

"The hardest part for me is not even so much that I have Parkinson's disease, it's my kids," said Schulman, who has an 11-year-old son, a 10-year-old son, a 7-year-old daughter and a 3-year-old son. Each knows in some way about their mother's disease.

"My oldest is aware. I sat with him once, and I talked to him about it, and he started crying actually, and he asked me if I was gonna die, and I said 'no, I'm not gonna die,' " she said. "The other ones know, but they don't really know so much about it.

"I cried a lot thinking now my kids are going to have a mom who is sick, someone who is not going to be able to do things they want me to do," she said. "I feel so bad for my husband. We've been married for 15 years, and now he has a wife with Parkinson's."

Most people die with Parkinson's disease, not because of it, says Factor. Still, people with very long-term Parkinson's can develop dementia or lose their ability to walk and then may get complications of immobility, such as pneumonia or other infections.

Join the conversation See the latest news and share your comments with CNN Health on Facebook and Twitter.

"They say you don't die from Parkinson's, but ..." Schulman said with a laugh. "I sort of disagree."

Everywhere on the groups she's joined -- a Facebook group and other chat rooms -- family members say their loved ones died from complications of the disease.

"I just hope that I progress slowly enough that there will be better medicine to help," she said.

Meanwhile, she still finds it embarrassing to say she has Parkinson's, because "people envision an old person shaking and looking a little funny."

"I want to be one of those personalities, those people who are like a fighter and gung ho and raising money and supporting the foundation and out there about it."

"I want to be that way," Schulman said. "I'm just not there yet."