Phelan-mcdermid syndrome

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What is the chance of having another child with Phelan-McDermid syndrome?

Most of the time Phelan-McDermid syndrome (PMS) is caused by a new deletion or disruption of the 22 chromosome; this means that it happened by chance and was not inherited from either parent. When this is the case the chance of having another child with PMS is extremely low.

However, about 20% of the PMS is caused by an unbalanced translocation. A translocation means that pieces of chromosomes break off and trade places. For example the tip of chromosome 22 may break off and the tip of chromosome 14 may break and then switch positions - so there is a piece of chromosome 22 attached to chromosome 14. That is an example of a balanced translocation, where all of the chromosome information is there but in different locations. If a parent passes on their 22 chromosome with the extra piece of 14 but also passes on their typical chromosome 14 then an unbalanced translocation occurs. The missing piece from chromosome 22 causes PMS and the extra piece of chromosome 14 may cause other symptoms. This can occur with any of the chromosomes (1-22 and/or the X and Y sex chromosome). In PMS about 50% of unbalanced translocations are new in the child and about half are inherited.

In order to find out if your child has an unbalanced translocation a karyotype (picture of chromosomes) should be ordered. To find out if either parent is a balanced carrier they will also need a karyotype. Being a balanced carrier will increase your chance of having another child with PMS. For more information talk with a genetic counselor or geneticist to talk with them.

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My child has learning difficulties and Phelan-McDermid syndrome, how can I help them?

What can I do to help my child with Phelan-McDermid syndrome meet developmental milestones?

Is genetic testing needed for a diagnosis of Phelan-McDermid syndrome?

What are the early symptoms of Phelan-McDermid syndrome?

Did my child inherit this from me?

What can I do for siblings of children with Phelan-McDermid syndrome?

Where can caregivers of people with Phelan-McDermid syndrome get support?

I have an appointment to see a genetic counselor about Phelan-McDermid syndrome, what should I expect?

What is the prognosis for individuals with Phelan-McDermid syndrome?

My child has learning difficulties and Phelan-McDermid syndrome, how can I help them?

The first step is to consider having your child diagnosed with a specific learning problem, this can help tailor assistance towards their specific needs. Your pediatrician or specialist may also have suggestions for interventions or resources that may help your child. Working with the school to set up an Individualized Education Program (IEP) for your child can help them learn and thrive in a school environment. There are resources available to help parents with children with learning difficulties such as the website Understood.

What can I do to help my child with Phelan-McDermid syndrome meet developmental milestones?
Is genetic testing needed for a diagnosis of Phelan-McDermid syndrome?

While a doctor may examine your child and suspect Phelan-McDermid syndrome (PMS) there are no clinical diagnostic criteria to make a definite diagnosis; genetic testing is needed to confirm the diagnosis. The most common genetic test which will find the deletion causing PMS is called a chromosomal microarray - which reads through the chromosomes to make sure there are no missing or extra pieces.

What are the early symptoms of Phelan-McDermid syndrome?

Not everyone with Phelan-McDermid syndrome (PMS) will have the same symptoms or signs. However, common symptoms of PMS can include developmental delay, intellectual disability (ranging from moderate to severe), low muscle tone, absent or severely delayed speech, and normal to accelerated growth.

Did my child inherit this from me?

Most of the time Phelan-McDermid syndrome (PMS) is caused by a new deletion or disruption of the 22 chromosome; this means that it happened by chance and was not inherited from either parent. When this is the case the chance of having another child with PMS is extremely low.

However, about 20% of the PMS is caused by an unbalanced translocation. A translocation means that pieces of chromosomes break off and trade places. For example the tip of chromosome 22 may break off and the tip of chromosome 14 may break and then switch positions - so there is a piece of chromosome 22 attached to chromosome 14. That is an example of a balanced translocation, where all of the chromosome information is there but in different locations. If a parent passes on their 22 chromosome with the extra piece of 14 but also passes on their typical chromosome 14 then an unbalanced translocation occurs. The missing piece from chromosome 22 causes PMS and the extra piece of chromosome 14 may cause other symptoms. This can occur with any of the chromosomes (1-22 and/or the X and Y sex chromosome). In PMS about 50% of unbalanced translocations are new in the child and about half are inherited.

In order to find out if your child has an unbalanced translocation a karyotype (picture of chromosomes) should be ordered. To find out if either parent is a balanced carrier they will also need a karyotype. Being a balanced carrier will increase your chance of having another child with PMS. For more information talk with a genetic counselor or geneticist to talk with them.

What can I do for siblings of children with Phelan-McDermid syndrome?

A child with Phelan-McDermid syndrome demands a lot of time and focus from parents. Although studies have shown that siblings of children with chronic illness tend to develop strong levels of compassion and empathy, these studies have also shown that siblings can develop feelings of jealousy and anger and high levels of anxiety. It is possible for healthy siblings to feel as if they have been pushed aside when parents focus more of their efforts on their child with a chronic illness. Parents should encourage healthy siblings to discuss their concerns and feelings about living with a sibling with a chronic illness. It is important for parents to acknowledge and address these concerns with their healthy children. Healthy siblings can feel more included in the family structure when they help with the care of their sick sibling. Parents are encouraged to make time for activities specifically for healthy siblings. Some siblings may benefit from support outside of the immediate family, such as meeting with a therapist. The Sibling Support Project is a nonprofit organization that serves the concerns and needs of siblings of people with special health, developmental, and mental health needs. There are also regional support groups for siblings of children with serious health conditions. Your child's pediatrician or your local hospital may be able to tell you if this type of support group is available in your area.

References
  • Houtzager BA, Oort FJ, Hoekstra-Weebers JE, et al. Coping and family functioning predict longitudinal psychological adaptation of siblings of childhood cancer patients. J Pediatr Psychol. 2004;29(8):591-605.
  • Barrera M. Siblings of Children with Rare Diseases are Psychosocially Vulnerable. [PowerPoint]. Vancouver, BC: Sibling Appreciation Day Children's Organ Transplant Society & Rare Disease Foundation; 2012.
Where can caregivers of people with Phelan-McDermid syndrome get support?

Taking care of someone with a long-term or chronic condition can be tiring and challenging and this is no different for parents or other caregivers of people with Phelan-McDermid syndrome. If you are a caregiver in need of support, try to take time for yourself, set aside time for personal counseling, or look for other resources at the Caregiver Action Network. This organization works to improve the quality of life for people who care for loved ones with chronic conditions, disabilities, disease, or the frailties of old age. Support groups can also help provide support and advice for caregivers such as the Phelan-McDermid Syndrome Foundation.

References
  • Caregiver Action Network website. http://caregiveraction.org/
I have an appointment to see a genetic counselor about Phelan-McDermid syndrome, what should I expect?

Genetic counselors are experts in both genetics as well as the psychosocial implications of having a genetic condition. The genetic counselor will sit down with you and your family and go through the family history, discuss the diagnosis of Phelan-McDermid syndrome, and help you work through what the diagnosis means for your family. Genetic counselors can help you talk with other family members about the diagnosis. Genetic counselors can also help you identify support resources available to you, and possibly even connect you with other families who are experiencing the same diagnosis. To learn more about genetic counselors and to find one near you visit the National Society of Genetic Counselors webpage.

What is the prognosis for individuals with Phelan-McDermid syndrome?

Not everyone with Phelan-McDermid syndrome will have the same symptoms. Most people with Phelan-McDermid syndrome will have severe speech delay/absent speech, developmental delay, and intellectual disability Almost all people with Phelan-McDermid syndrome will need assistance for daily living and will require medical support throughout their life. Individuals with Phelan-McDermid syndrome survive into adult life. Contact the Phelan-McDermid Syndrome Foundation to find ways to get in contact with other families who have family members with Phelan-McDermid syndrome.

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