Caregivers of Children With AADC Deficiency Share Daily Experiences

Children with aromatic l-amino acid decarboxylase (AADC) deficiency experience a wide range of symptoms and difficulties in day-to-day activities, which can have substantial affects on their quality of life, a study based on interviews with caregivers reported.

This is the first published scientific study to explore the qualitative experience of living with AADC deficiency, according to its researchers.

The study, “Symptoms and impact of aromatic l-amino acid decarboxylase (AADC) deficiency: A qualitative study and the development of a patient-centred conceptual model,” was published in Current Medical Research and Opinion. 

The study was funded by PTC Therapeutics, which is developing PTC-AADC, an investigative gene therapy for people with AADC deficiency.

AADC deficiency, a rare disease, is characterized by a lack of the AADC enzyme, which normally is needed to make certain signaling molecules in the brain (neurotransmitters). Its symptoms are well described in scientific literature; however, few studies have directly assessed the experiences of people living with the disease.

But no qualitative studies have been done in AADC deficiency. A team of six researchers, which included three PTC employees, set out to conduct such a study.

“Qualitative research allows for an in-depth exploration of the impact of a disease from the perspective of the participant, such as a patient or caregiver,” the researchers wrote. “In qualitative research, participants are given the opportunity to speak freely about their experiences outside the constraints of closed question surveys or questionnaires. This generates rich data which can highlight symptoms and impacts that were previously unknown.”

These scientists added that qualitative research is especially important for rare diseases like AADC deficiency, “as it enables a deeper understanding of the burden of disease and provides patients and caregivers with a voice.”

They conducted interviews with caregivers of children with AADC deficiency living in Italy, Portugal, Spain, and the U.S. In total, 14 caregivers were interviewed: 10 mothers, two fathers, an aunt, and a brother. The interviewees cared for 13 children (two caregivers were parents of the same child), whose ages ranged from 1 to 15.

From the interviews, the researchers highlighted common themes that emerged. For example, many caregivers reported that their children had substantially impaired motor function, though the extent varied — some were not able to hold their head up; others were able to walk, though usually to a very limited extent.

“He has no muscle tone … he cannot control his head, his arms, his legs, he cannot control his motion,” said one caregiver of a 10-year-old.

“He probably could take a good, 10 footsteps, maybe with no support, going very slow … I’m more, holding him with a hand to give some strength, but I’m not supporting him to walk,” said another, who cares for a 6-year-old.

Many caregivers also reported substantial fatigue in their children.

“Imagine you have just run a marathon and you’re exhausted and tired, so, you take a few steps, and you want to lean for support. That’s kind of imagining living a life like this. The fatigue is always extreme,” one caregiver said.

Cognitive and communication difficulties were commonly identified. While most caregivers reported that their children could not speak — and those that did mostly used only short phrases or words — the children were able to communicate by making noises, or using gestures or eye movements.

“She is not able to talk … but she communicates with us with her eyes,” said the caregiver of a 15-year-old.

“It’s not necessarily that they’re mentally incapable or that they don’t understand, because they do understand. … I see in his eyes that he recognizes and knows things more than he can use and communicate to me,” said another, who cares for a 4-year-old.

Most caregivers described their child’s cognitive abilities as varying, “depending on whether they were having a good day or bad day.”

A variety of other symptoms also were reported, including digestive problems, sleep difficulties, seizures, and oculogyric crises (abnormal movements of the eyeballs, usually to a fixed “looking up” position).

These symptoms had substantial impacts on children’s day-to-day lives. Caregivers frequently said that children had difficulty engaging in play and socializing with peers.

“He can’t play with other children, because he can’t really walk [or] hold his head up … he can’t like actively participate with other toddlers his age,” said the caregiver of a 2-year-old.

Emotional struggles — particularly frustration when desires outpaced abilities — also were common.

“It can be really frustrating with the inability to verbalise or the inability to engage in something physical,” said the caregiver of a 4-year-old.

Caregivers also reported a variety of strategies to manage their child’s disease. These ranged from using a wheelchair or other mobility device to help children get around, to taking medications to ease the impact of sleep problems, pain, and seizures, to physical and occupational therapy to aid in day-to-day living.

“[This study is] the first qualitative with caregivers study to describe the broader life experience of individuals with AADC deficiency, highlighting the experiences they are able to have and those which they miss out on,” the researchers concluded.

They called for further research into the lived experiences of people with AADC deficiency, and into finding therapies to improve disease management.