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Learn why ring chromosome 22 matters for individuals with Phelan-McDermid syndrome (PMS). While most people with PMS caused by a deletion have a terminal 22q13 deletion, approximately 10% have a ring chromosome 22, in which the ends of chromosome 22 join to form a circle. This blog explains why families should know whether a loved one with a terminal deletion has ring 22 and why a karyotype or FISH testing may be needed to identify it. Ring chromosome 22 can have additional medical implications, including an increased risk for tumors associated with loss of function of the NF2 gene and NF2-related schwannomatosis. Understanding a person’s genetic diagnosis can help families and healthcare providers discuss appropriate medical monitoring and recognize potential concerns earlier. Families affected by Phelan-McDermid syndrome can learn what testing identifies ring chromosome 22 and why follow-up with genetics and other specialists may be important.
Looking for Phelan-McDermid Syndrome Foundation apparel? The official PMSF online store makes it easy to show your support, spread awareness, and stay connected to the Phelan-McDermid syndrome community
Phelan-McDermid syndrome is a rare genetic condition usually caused by a deletion or structural change at the end of chromosome 22, in a region called 22q13. Symptoms and severity can vary widely among people with Phelan-McDermid syndrome. For individuals with a chromosome 22 deletion, the size of the deletion may help explain some of these clinical differences. In general, larger 22q13 deletions are associated with more significant developmental delays and medical concerns. A recent study in 63 people with Phelan-McDermid syndrome further explored these genotype-phenotype relationships, helping researchers better understand how chromosome 22 deletion size may influence symptoms such as language development, motor function and development, and social behaviors as well as medical issues. This study also identified several candidate genes that could also be contributing to the symptoms seen in Phelan-McDermid syndrome.
Researchers at Ulm University in Germany have identified two promising blood-based biomarkers for Phelan-McDermid syndrome, including SHANK3 protein and beta-synuclein. In a pilot study of 23 individuals with Phelan-McDermid syndrome, lower SHANK3 levels and higher beta-synuclein levels were found compared to typically-developing controls. Individuals with Phelan-McDermid syndrome who had a history of regression had lower SHANK3 levels, and those with more significant language impairments had higher beta-synuclein levels. These findings also were observed in a Shank3 mouse model. Together, this suggests SHANK3 and beta-synuclein may be potential blood-based biomarkers in Phelan-McDermid syndrome. Although larger studies are needed to confirm the results, this research marks an important step toward identifying objective biological-based measures that may relate to disease severity and help monitor progression and evaluate treatment effectiveness.
The Castillo family’s 9th Annual #TeamMatthewLuis fundraiser raised more than $21,000 for Phelan-McDermid syndrome research and family support programs.
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