A genetic disorder that occurs quite rarely and causes medical, behavioral, and intellectual problems is called Phelan-McDermid Syndrome (PMS). Usually, people begin to experience symptoms early in life that range from mild to severe. For example, muscle weakness, seizures, developmental delays, speech problems, certain physical features, and others. Furthermore, some people may develop autism spectrum disorder. Some healthcare professionals may call this disorder 22q13.3 deletion syndrome.
PMS occurs quite rarely and affects about 2 to 10 of every 1 million births. Moreover, in most cases, it is challenging to diagnose this condition. Nowadays, about 2,200 to 2,500 people are diagnosed with PMS in the entire world.
Symptoms
Usually, the signs and symptoms of people with PMS vary widely. Moreover, the symptoms and different physical features can appear at birth, during infancy, or in early childhood. Check below some symptoms that children with PMS often experience:
- Hypotonia (weakness of the muscles)
- Developmental delays
- High pain tolerance
- Sleep disorders (such as insomnia)
- Speech problems (such as absent or delayed ability to talk)
- Difficulty swallowing or eating
- Gastrointestinal (GI) problems (including frequent nausea or vomiting) or gastroesophageal reflux disease (GERD)
- Dehydration
Check below also some physical characteristics of people with this disorder:
- Ptosis (drooping eyelids)
- Syndactyly (fusion of the second and third toes)
- Long and narrow head
- Abnormal toenails
- A pointed chin
- Large hands or feet
- Large ears
- Deep-set eyes
Rarely, PMS can involve congenital heart disorders, kidney problems, or arachnoid cysts (fluid-filled sacs that develop on the brain). In such cases, they may also experience pressure in the head, which often causes irritation, crying, headaches, and seizures (epilepsy).
A lot of children with PMS may also have autism spectrum disorder, which may also cause additional behaviors. These include:
- Avoiding direct eye contact
- Obsessively chew things that are not food
- Increased sensitivity to touch
- They may also experience anxiety, especially in social situations
It is very important to see a healthcare professional if any of the previous symptoms occur. Leaving this condition untreated can lead to serious and even life-threatening complications.
Causes
Healthcare professionals have determined that the disorder occurs due to a chromosome deletion. That’s why it is sometimes called a chromosomal deletion syndrome. In general, the chromosomes are specific structures inside cells that contain DNA. DNA holds instructions that tell cells when to grow, multiply, and die. Furthermore, they also determine your traits (including height, eye color, and risk for diseases).
Normally, in humans, cells contain 23 pairs of chromosomes, for a total of 46. In people with PMS, a part of chromosome 22 is missing, “deleted”. In addition, most diagnosed cases are not inherited. The deletion of this part of the chromosome occurs randomly during fetal development. Rarely, the abnormal gene that causes this disorder can be inherited. For instance, if you have a parent who has this abnormal gene, there is a 50% chance of passing it to your child.
Complications
People with PMS may also experience some complications, especially if they leave the disorder untreated. Check below some potential complications of this disorder:
- Autism spectrum disorder
- Seizures
- Developmental delays
- Low muscle tone (also known as hypotonia)
- GERD
- Insomnia (sleep disturbances)
- Reduced sensitivity to pain
- Vision disorders
- Lymphedema
- Problems with the heart and kidneys
- Recurrent ear infections
- Zinc deficiency (rarely)
This article does not contain a full list of PMS complications. Discuss it with your healthcare professional for more details and about measures to prevent them.
How to Prevent Phelan-McDermid Syndrome?
Unfortunately, there is no way to prevent this condition because it is not possible to repair the genetic changes that cause PMS. Rarely, people with this disorder can choose IVF (in vitro fertilization) or perform genetic tests to make sure they do not have this abnormal gene. However, it is very important to understand the risks of having children with Phelan-McDermid syndrome. You can also consult with a genetic counselor to understand the chances of passing the abnormal gene.
Diagnosis
If your physicians notice signs that resemble PMS, they begin the diagnosis with the following steps. Examples include:
- Physical examination
- Evaluation of the medical and family history of the child
- Questions about the symptoms
- Genetic testing to check for chromosomal deletion
Rarely, this disorder can be caused by a DNA change in the SHANK3 gene. When deletion of the chromosome is not found, physicians may recommend additional genetic tests to check for the abnormal SHANK3 gene.
Once you are diagnosed with 22q.13.3 deletion syndrome, doctors may perform additional tests. These include:
- Renal ultrasound to check for kidney defects
- Echocardiogram to look for heart problems
- Eye examination
- Sleep study
- Hearing evaluation
- Other imaging tests to check the child’s brain for arachnoid cysts, such as MRI (magnetic resonance imaging) or CT (computerized tomography) scans
Treatment
Unfortunately, this condition cannot be cured. That’s why the treatment goal is to relieve the symptoms, prevent life-threatening complications, and improve your child’s quality of life. Usually, your children with PMS require a healthcare team. These include:
- Nephrologists
- Neurologists
- Gastroenterologists
- Cardiologists
- Physical and occupational therapists who help improve performance with daily activities (such as writing and eating)
- Speech and language pathologists
- Endocrinologists
- Orthopedists and others
Additional Care
You should take your child to all appointments with healthcare professionals to improve function. Furthermore, it is advised to protect your child from direct UV (ultraviolet light), keep him/her hydrated, and avoid extreme heat because of the reduced ability to sweat, which is common in children with PMS. However, most people with PMS have an increased tolerance to pain and difficulties with communication. Thus, you should stay alert to help your child. Check below for some signs that may indicate pain:
- Being more irritable than previously
- The body, arms, or legs are rigid
- Yelling or moaning
- Specific facial expressions (such as grimacing, holding their eyes tightly shut, or pursing their lips)
- Fast breathing
- Reduced activity
Consult with your physician for more details.
Frequently Asked Questions
What is the outlook for my children if they have Phelan-McDermid syndrome?
The prognosis of this disorder is different among people because it depends on several factors. These include the severity of the condition and symptoms, other health problems, and age. In any case, with treatment, this disorder rarely causes life-threatening health problems.
What is the life expectancy of someone with Phelan-McDermid syndrome?
In general, the life expectancy of people with PMS varies because it depends on multiple factors. While some sources showed an increased risk of early mortality, with proper treatment, most problems can be resolved.
What are the symptoms of Phelan-McDermid syndrome?
Check below for the most common symptoms of this disorder:
- Developmental delays
- Intellectual disabilities
- Motor skill deficit
- Autism spectrum disorder
- Minor dysmorphic features
Do not hesitate to contact your doctor if you notice your child experiences any of the previous symptoms. Ask your healthcare provider if you have additional questions.
