Actor Colin Farrell is launching a new foundation to raise awareness of a rare genetic condition called Angelman syndrome, so that his son and others with the disorder will have more support and resources as they transition into adulthood.

"I want the world to be kind to James," Farrell, 48, told People magazine ahead of his son’s 21st birthday in September.

"All the safeguards that are put in place, special ed classes — that all goes away, so you’re left with a young adult who should be an integrated part of our modern society and, more often than not, is left behind." 

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The syndrome was first described in 1965 by physician Dr. Harry Angelman, according to the National Organization for Rare Disorders (NORD).

It is a disorder of the nervous system, which helps control movements, thoughts and behaviors, as stated by Cleveland Clinic.

Most cases are caused by a random genetic change during early development, which means those who are affected usually have no family history of the disease, the National Institutes of Health (NIH) adds.

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"Angelman syndrome is a complex neurodevelopmental disorder resulting from the loss of function of a specific gene called UBE3A, which plays a crucial role in brain development," Dr. Issac Molinero, pediatric neurologist at Ochsner Children’s Hospital in New Orleans, Louisiana, told Fox News Digital.

The genetic changes that occur with Angelman syndrome lead to significant challenges, including severe intellectual disability, communication difficulties and characteristic behavioral patterns, such as frequent laughter and smiling, according to Molinero.

Dr. Dana Price, pediatric neurologist and director of Angelman Clinic at NYU in New York City, described the disorder as a "spectrum."

It can include "low muscle tone, developmental delay, poor gait, seizures (ranging from febrile seizures to refractory epilepsy), constipation, poor sleep and challenging behavior," she told Fox News Digital in an email.

The condition causes delays in development for the children it affects.

Newborn babies may have trouble latching on or swallowing milk, and after a few months, they may not be able to lift their heads, according to Cedars Sinai.

They may also miss the milestones of sitting up alone, crawling, standing up by themselves or taking their first steps.

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Infants can develop microcephaly, a condition where their heads are characteristically smaller compared to other children of the same age, per NIH.

"Generally, developmental delays associated with Angelman syndrome will become noticeable around six to 12 months of age," Molinero told Fox News Digital.

Silence is another hallmark clue, experts say. 

The baby may be able to say words like "Dada" and follow simple commands, but won’t be able to put together complete sentences or have a verbal conversation, according to Cedars Sinai.

At age 2 or 3 years old, some children may start to have seizures, Mayo Clinic notes.

One typical hallmark of the syndrome is unprovoked fits of laughter, along with frequent smiling and hand-flapping movements, according to NIH. 

Children with the disorder often have short attention spans, with most having difficulty sleeping or needing less sleep than normal.

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The sleep issues tend to improve as the child gets older, but the limited speech, intellectual disabilities and seizures may continue throughout life.

Although most people with the condition can’t speak, they learn to communicate in other ways, such as gesturing, and may be able to understand a simple conversation, according to NORD.

Doctors diagnose the condition based on blood tests that look for the genetic mutation, experts say.

The syndrome is often misdiagnosed, as initial symptoms can be confused with more well-known diseases like autism or cerebral palsy, according to the Angelman Syndrome Foundation.

Children are often not diagnosed until they are 3 or 4 years old, when they have already started pre-school, experts say.

The rare disorder only affects roughly 500,000 people worldwide, Molinero noted.

Those with the condition have a normal life expectancy, according to NIH.

"Although there is no definitive cure for Angelman syndrome, proactive early intervention through therapies, educational support and community resources can significantly enhance the quality of life for affected individuals and their families," Molinero said.

Depending on symptoms, treatments may include various medications for seizures, sleep, mood, reflux and constipation, Price added.

Those with the disorder may also receive various types of therapy to learn how to communicate non-verbally, to manage hyperactivity and to improve balance.

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"This is a very exciting time to work with the Angelman Community, because drug companies are working to develop precision medicine to turn on the missing gene (UBE3A)," Price said.

"Genetic treatment with precision medicine is such a revolutionary prospect — for the first time, we would be treating the disease, not the symptoms."

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Those who have a family member with Angelman Syndrome or are affected themselves can visit an Angelman Clinic or the Angelman Syndrome Foundation’s website at https://www.angelman.org.

Fox News Digital reached out to the Colin Farrell Foundation for comment.