The family of Nóra Quoirin described her as a "fun, funny, and extremely loving" person who was looking forward to her holidays in Malaysia.
In a statement to RTÉ News, they spoke about Nóra's special needs, which affected her mental and physical capability.
They said: "She is not like other teenagers. She is not independent and does not go anywhere alone.
"Nora was born with holoprosencephaly - this means that she has a smaller brain. All her life she has spent a lot of time in hospital.
"Her verbal communication is limited. She is unable to do maths and so things like money are impossible to manage.
"She cannot make or receive phone calls independently. She can wash and dress herself, though she cannot manage buttons, and struggles to wash her hair."
"Nóra is a very special person. She is fun, funny, and extremely loving. With her family, she is very affectionate - family is her whole world and she loves to play games, like Cat Bingo, with us. She likes to tell us silly jokes and wear clever, colourful t-shirts. She is not like other teenagers. She is not independent and does not go anywhere alone.
"Nóra was born with Holoprosencephaly; this means that she has a smaller brain. All her life she has spent a lot of time in hospital. When she was born, she needed operations to help her breathing. She has specialists that monitor her growth, her physical abilities and her strength, and especially her mental capacity. Nóra has always needed dedicated specialist educational provision, and now attends a school for children and young people with learning and communication difficulties.
"Nóra and her family are bi-lingual and bi-cultural. Nóra is very proud that she can speak French as well as English. But her verbal communication is limited. Nóra can read like a young child, but she cannot write more than a few words. She has a good memory but she cannot understand anything conceptual. She is unable to do maths and so things like money are impossible to manage. She cannot make or receive phonecalls independently.
"She can wash and dress herself, though she cannot manage buttons, and struggles to wash her hair. At school, she is learning to ride a bicycle properly. Nóra likes to walk with her family, but her balance is limited and she struggles with coordination. She has been to Asia, and many European countries before, and has never wandered off or got lost.
"Nóra is very sensitive. Outside the family, Nóra is very shy and can be quite anxious. Every night, her special time is for cuddles and a night-time story with her Mum. And she was extremely excited about the family holiday in Malaysia."
"That is the end of the statement. The family would again like to take this opportunity to express their sincere thanks to the Royal Malaysian Police, and all those searching for Nóra. Some of these people have been working all day, every day and the family cannot express their gratitude enough."