Phelan-McDermid Syndrome (PMS) is a rare genetic disorder impacting brain development and overall body function. It arises from a specific genetic change, leading to a range of intellectual and physical challenges that vary considerably among individuals. Ongoing medical attention and supportive care are often required throughout their lives.
Understanding the Genetic Basis
Phelan-McDermid Syndrome primarily results from a deletion on the long arm of chromosome 22 at region 22q13.3, meaning a small piece of genetic material is missing. In some instances, it can also be caused by a pathogenic variant within the SHANK3 gene, located in this deleted region.
The SHANK3 gene plays a significant role in brain development and function, particularly in forming and maintaining synapses, the connections between nerve cells. When altered or missing, it disrupts these brain connections. While most cases occur spontaneously, about 20% can be passed down from a parent carrying a related genetic change.
Recognizing the Characteristics
Individuals with Phelan-McDermid Syndrome often experience global developmental delays, affecting motor skills, cognitive abilities, and overall development. Intellectual disability is a common feature, ranging from mild to severe, impacting learning and problem-solving. These delays can be among the first noticeable symptoms, prompting families to seek diagnosis.
Speech and communication challenges are prominent, with many individuals having absent or severely limited verbal speech. Alternative communication methods often become necessary. Behavioral traits resembling autism spectrum disorder are also frequently observed, including repetitive behaviors, sensory processing difficulties, and social interaction challenges.
Physical characteristics can include low muscle tone (hypotonia), often present at birth or in early infancy. Distinct facial features may also be present, though their presentation varies widely. Other associated medical conditions include seizures, gastrointestinal issues, sleep disturbances, and kidney problems.
Diagnosis and Early Identification
Diagnosis of Phelan-McDermid Syndrome involves specific genetic testing. Chromosomal microarray (CMA) is a common test to detect the 22q13.3 deletion. Fluorescence in situ hybridization (FISH) is another genetic test that can identify this deletion.
In some cases, whole exome sequencing may identify pathogenic variants within the SHANK3 gene when the deletion is not present. Early diagnosis is important, allowing for timely initiation of interventions and support services that can significantly improve developmental outcomes.
Supportive Care and Management
Managing Phelan-McDermid Syndrome involves a multidisciplinary approach with therapies tailored to individual needs. Speech therapy often incorporates augmentative and alternative communication (AAC) strategies. Occupational therapy focuses on developing fine motor skills and daily living activities, while physical therapy addresses gross motor skills and muscle strength.
Behavioral interventions address challenging behaviors and promote positive social interactions. Medical management is provided for associated conditions, such as anti-seizure medications for epilepsy, dietary adjustments for gastrointestinal issues, and strategies to improve sleep. Individualized educational plans (IEPs) are developed to support academic learning, and family support networks offer resources and guidance.
Living with Phelan-McDermid Syndrome
The long-term outlook for individuals with Phelan-McDermid Syndrome centers on ongoing support and community involvement. Many will require continuous care and assistance throughout their lives. Advocacy groups, such as the Phelan-McDermid Syndrome Foundation, connect families, provide resources, and fund research. These organizations foster a sense of community and shared experience.
Research efforts are continuously underway, aiming to deepen understanding of the syndrome’s mechanisms and develop targeted therapies. These advancements offer hope for improved treatments and enhanced quality of life.