It’s certain we’ll be hearing a lot more about Phelan McDermid syndrome (PMS) over the next few months so I thought some more detailed insight into the condition could be of value.
Fortuitously, results of a survey were published in July this year, titled Parental perspectives on Phelan-McDermid syndrome: Results of a worldwide survey.
The European Phelan-McDermid syndrome guideline consortium created a survey for parents of individuals with PMS to collect their lived experiences with care needs, genotypes, somatic issues, mental health issues and parental stress.
The authors describe Phelan-McDermid syndrome, also known as 22q13.3 deletion syndrome, as a rare neurodevelopmental disorder characterised by low muscle tone, absent or delayed speech and moderate to severe intellectual disability. Approximately 65% of individuals with PMS are also diagnosed with Autism Spectrum Disorder and other mental health issues such as mood disorders.
In total, 587 surveys from 35 countries worldwide were completed and analysed. Roughly half of the responses came from Europe and a third from North America. The median age was 12 years, with median age at diagnosis of 3 years. Slightly more females than males were represented.
The percentage of individuals who received treatment at a local/regional hospital or a centre of expertise for PMS/rare syndromes did not differ significantly between the United States and Europe – roughly 10% of individuals in North America and Europe were treated at a centre of expertise and 25-35% at academic hospitals.
The most prevalent issues, impacting more than a third of the PMS population, were problems with speech and communication (97%), learning difficulties or intellectual disability (95%), problems with fine motor skills (83%), problems with attention and concentration (80%), low pain perception (78%), low muscle tone (77%), problems with gross motor skills, such as walking (74%), general behavioural problems (71%), sleeping problems (57%), problems with flexibility and adapting to change (50%), constipation (48%), problems with regulating body temperature (47%), hyperactivity (46%), anxious behaviour (41%), obsessions (35%), problems with feet (34%) and swallowing difficulties (33%).
Prevalence of symptoms can vary significantly with age – while the prevalence of low muscle tone decreases with age, prevalence of problems such as epilepsy, sleeping issues, regression, mood issues and severe psychiatric issues increases with age.
Epilepsy impacted 19% of 4-12 year olds (but increased to 43% in those aged >18 years) and had a significant association with intellectual disability and sleeping issues.
Stress was relatively high among the parents of individuals with PMS. The most stressful child-related factor for parents (61.2%) was “not knowing what is bothering my child due to limited communication possibilities”. This item was significantly associated with a younger age (<12 years) in individuals with PMS (p = 0.017).
Neuren’s Phase 2 study of NNZ-2591 in the treatment of Phelan McDermid syndrome has been conducted in 20 males and females aged 3 to 12 years.
Neuren’s study has used 14 exploratory efficacy outcome measures, including Phelan-McDermid syndrome-specific Clinical Global Impression Scales designed by long-term PMS experts in work funded by Neuren. These experts chose “anchors” based on symptoms which are relevant to PMS in the areas of communication, motor skill, social interaction, self-care, and cognition/learning.
Another measure is said to be in progress which focuses on other symptom areas such as GI, sleep, seizures, sensory and behaviour.
(20min delay)