A six-year-old boy is asking strangers to send him Christmas cards to cheer him up while he spends the holiday at a hospital waiting for a heart transplant.

Carlos Rolon, of Worcester, Massachusetts, was diagnosed when he was born with a heart abnormality known as unbalanced atrioventricular canal defect.

He had four open heart surgeries by the time he was two years old and has been waiting for a transplant for three-and-a-half years, reported Boston 25 News.

Carlos was admitted to Boston Children's Hospital in August after suffering an infection that was making him vomit daily.

Doctors say he is not allowed to go home until he has a transplant, and Carlos is now asking for cards so he can decorate his room.

Carlos Rolon, six, of Worcester, Massachusetts, is asking for Christmas cards to decorate his room at Boston Children's Hospital. Pictured: Carlos meeting Santa Claus

Carlos (left and right) was born with unbalanced atrioventricular canal defect. It is a heart defect that occurs when there is a hole in the wall between the upper two chambers, which affects blood flow

Carlos's mother, Sheena Cossette, told Boston 25 News that she learned of her son's medical condition mid-way through her pregnancy.

'They had told us there was a probability of five surgeries by the age of five,' she said.

'Carlos had four by the age of two, and then it was shut down and determined that transplant would be the best option.'

He was diagnosed with an unbalanced atrioventricular canal defect, which occurs before birth as the baby's heart is developing.

A normal, healthy heart has four chambers and valves control the blood flow in and out of those chambers.

The two chambers on the right send blood to the lungs and the two chambers on the left receive the blood back from the lungs that has been enriched with oxygen.

In Carlos's case, there is a hole in the wall between the heart's upper two chambers and the valve between the upper and lower chambers leaks.

This can cause increased blood flow, pressure buildup in the lungs, and susceptibility to lung infections.

It occurs in two out of every 10,000 newborns, according to Boston Children's Hospital.

In some cases, the hole can be surgically repaired, but, in others, a heart transplant may be necessary.

He had four open heart surgeries by the time he was two years old before doctors determined he needs a new heart. Pictured: Carlos, as a newborn, with his mother, Sheena Cossette

Carlos (left and right) was hospitalized in August after an infection that caused him to vomit every day. Doctors told his family he is not well enough to leave the hospital until he gets a new heart

In August, his mother rushed him to Boston Children's after he vomited every day for several days.

He was diagnosed with an infection, the details of which are unclear, and told that because of his fragile condition, he's not allowed to leave until he has a new heart.

This Monday marks Carlos's 99th day in the hospital.

Cossette says Christmas is her son's favorite holiday and he is hoping he can decorate his hospital room with cards.

'He sees a lot of the kids come and go, and he's starting to question when he's going to get to go, and we tell him when he gets a new heart,' she told Boston 25 News.

'But with the holidays coming, we're trying to make it as best as we can here.'

Cossette posted a video to her Facebook page on Wednesday afternoon of Carlos asking for the cards.

In the clip, he asks: 'Can you send me - mail me - some, some, some, some Christmas cards please? Thank you!'

The 41-second video has been viewed more than 17,000 times and has been shared more than 600 times.

Because of Carlos's size, his new heart needs to come from a child donor. Pictured: Carlos, left, with his mother

As of Monday, December 9, Carlos (left and right) has spent 99 days in the hospital. Christmas is his favorite holiday and he hopes Christmas cards will cheer him up

Because Carlos is so small, the donor has to be a child. But doctors are hopeful now that he is at the top of the list.

'I’m praying for a Christmas miracle,' Cossette told Boston 25 News.

'Unfortunately, with that being said, another child has to pass. If I had a message to send to anyone...if you did want to donate, you would be saving someone else's life and, parents like me who are waiting, that would be one of the greatest gifts you could give.'

Cossette has set up a fundraiser on Facebook to help raise money for Carlos's hospital stay. As of Monday afternoon, $1,885 had been raised out of a $2,500 goal.

If you would like to send Christmas cards to Carlos, please mail to:

Boston Children's Hospital

Cardiac Unit 8 East

c/o Carlos Rolon

300 Longwood Avenue

Boston, MA 02115