Phelan-McDermid Syndrome (22q13 Deletion) in Babies
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published NIH, NORD, PMS Foundation guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect phelan-mcdermid syndrome (22q13 deletion) in babies, here is what the evidence says.
The short answer
Phelan-McDermid syndrome (PMS) is a genetic condition caused by a deletion or mutation affecting the SHANK3 gene on chromosome 22q13. It is characterized by significant speech delay or absence of speech, low muscle tone (hypotonia), features of autism spectrum disorder, and reduced perception of pain. Many children chew on non-food items (mouthing behavior). PMS is often initially misdiagnosed as idiopathic autism. Seizures develop in many individuals, sometimes not until adolescence. Diagnosis is made through chromosomal microarray or targeted SHANK3 gene sequencing.
Key takeaways
- Phelan-McDermid syndrome (PMS) is a genetic condition caused by a deletion or mutation affecting the SHANK3 gene on chromosome 22q13. It is characterized by significant speech delay or absence of speech, low muscle tone (hypotonia), features of autism spectrum disorder, and reduced perception of pain. Many children chew on non-food items (mouthing behavior). PMS is often initially misdiagnosed as idiopathic autism. Seizures develop in many individuals, sometimes not until adolescence. Diagnosis is made through chromosomal microarray or targeted SHANK3 gene sequencing.
- Usually normal when: Your child was evaluated for Phelan-McDermid syndrome and chromosomal microarray and SHANK3 testing were normal
- Call your doctor if: Your child with PMS has a seizure, staring spells, or episodes of unresponsiveness
- Varies by age — see the age-by-age breakdown below
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What Parents Should Know
According to NIH, NORD, PMS Foundation guidelines, phelan-McDermid syndrome (PMS) is a genetic condition caused by a deletion or mutation affecting the SHANK3 gene on chromosome 22q13. It is characterized by significant speech delay or absence of speech, low muscle tone (hypotonia), features of autism spectrum disorder, and reduced perception of pain. Many children chew on non-food items (mouthing behavior). PMS is often initially misdiagnosed as idiopathic autism. Seizures develop in many individuals, sometimes not until adolescence. Diagnosis is made through chromosomal microarray or targeted SHANK3 gene sequencing. At 0-6 months, babies with Phelan-McDermid syndrome are typically floppy (hypotonic) from birth, which may cause feeding difficulties and delayed motor milestones. Growth is usually normal or even above average. The facial features are generally mild and may include full or puffy eyelids, pointed chin, prominent ears, and long eyelashes. Some babies have minor hand and foot differences. If a chromosomal microarray is done for hypotonia or developmental concerns, the 22q13 deletion may be identified. Some cases result from SHANK3 point mutations that require gene sequencing to detect. It is generally considered normal when your child was evaluated for Phelan-McDermid syndrome and chromosomal microarray and SHANK3 testing were normal. However, you should contact your pediatrician promptly if your child with PMS has a seizure, staring spells, or episodes of unresponsiveness.
Normal vs. Concerning
When to Seek Immediate Care
- Your child with PMS has a seizure, staring spells, or episodes of unresponsiveness
- Your child with PMS is losing previously acquired skills (regression in speech, motor abilities, or self-care)
- Your child with PMS has injured themselves without showing a pain response and may have a significant injury (fracture, burn) that went unnoticed
- Your child is having severe behavioral changes, prolonged mood episodes, or signs of a psychiatric crisis
By Age
What to expect by age
0-6 months
Babies with Phelan-McDermid syndrome are typically floppy (hypotonic) from birth, which may cause feeding difficulties and delayed motor milestones. Growth is usually normal or even above average. The facial features are generally mild and may include full or puffy eyelids, pointed chin, prominent ears, and long eyelashes. Some babies have minor hand and foot differences. If a chromosomal microarray is done for hypotonia or developmental concerns, the 22q13 deletion may be identified. Some cases result from SHANK3 point mutations that require gene sequencing to detect.
6-18 months
Motor delays become more apparent, though many children eventually learn to walk (average age 22 months, but some much later). The most striking feature is significant delay in or complete absence of babbling and early speech. Babies may seem unusually tolerant of pain - not crying when injured, not reacting to blood draws, or not showing discomfort that would be expected. Mouthing and chewing on non-food objects (hands, clothing, toys) is very common. Poor eye contact and reduced social reciprocity may raise concerns about autism.
18 months - 3 years
Absence of speech or very limited speech is the hallmark of PMS at this age. Many children are diagnosed with autism spectrum disorder before the genetic cause is identified. Requesting chromosomal microarray testing is important for any child with significant speech delay combined with hypotonia and autistic features. Augmentative and alternative communication (AAC) devices can be very helpful. Behavioral features include hand flapping, poor eye contact, and sensory seeking. Gastroesophageal reflux and constipation are common. Renal (kidney) abnormalities occur in about 40% and should be screened.
3 years+
Seizures develop in approximately 25-50% of individuals, sometimes not until adolescence or adulthood. Some individuals experience regression (loss of previously acquired skills), particularly during adolescence, which may be associated with onset of seizures or bipolar-like episodes. Ongoing therapies (speech, occupational, physical, behavioral) are beneficial. Research into targeted treatments for SHANK3-related disorders is active, with several clinical trials underway. Many individuals require lifelong support but can develop meaningful communication and social connections.
What to Tell Your Pediatrician
- Describe when you first noticed phelan-mcdermid syndrome (22q13 deletion) in babies and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your child has significant speech delay, hypotonia, and autistic features and has not had chromosomal microarray testing.
- Mention if your child with PMS seems to have reduced pain perception and you need guidance on safety measures.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your child was evaluated for Phelan-McDermid syndrome and chromosomal microarray and SHANK3 testing were normal
- Your child with PMS is making steady progress with communication using AAC or sign language
- Your child with PMS has had appropriate seizure screening and monitoring with no seizures detected
- Your child has significant speech delay, hypotonia, and autistic features and has not had chromosomal microarray testing
- Your child with PMS seems to have reduced pain perception and you need guidance on safety measures
- Your child with PMS is persistently mouthing or chewing on objects and you need strategies for redirecting this behavior safely
- You want to discuss genetic testing results, recurrence risk, or available clinical trials
- Your child with PMS has a seizure, staring spells, or episodes of unresponsiveness
- Your child with PMS is losing previously acquired skills (regression in speech, motor abilities, or self-care)
- Your child with PMS has injured themselves without showing a pain response and may have a significant injury (fracture, burn) that went unnoticed
- Your child is having severe behavioral changes, prolonged mood episodes, or signs of a psychiatric crisis
What You Can Do at Home
- Keep track of when you notice phelan-mcdermid syndrome (22q13 deletion) in babies — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your child was evaluated for Phelan-McDermid syndrome and chromosomal microarray and SHANK3 testing were normal — this is generally within the range of normal.
- At 0-6 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
- While monitoring at home, seek immediate care if your child with PMS has a seizure, staring spells, or episodes of unresponsiveness.
Related Conditions
Early Signs of Autism in Babies and Toddlers
Autism spectrum disorder (ASD) can sometimes be identified as early as 12-18 months, though most children are not diagnosed until age 2-3. Early signs include limited eye contact, not responding to their name, lack of pointing or showing, limited social smiling, and absence of pretend play. Having one or two of these signs does not mean your child has autism - many typically developing children share individual traits. However, a pattern of multiple social communication differences warrants evaluation. Early intervention, regardless of eventual diagnosis, consistently leads to the best outcomes.
Low Muscle Tone (Hypotonia)
Low muscle tone means your baby's muscles feel less firm or their body feels "floppy" when you hold them. While it can sometimes indicate an underlying condition, many babies with mildly low tone do very well with support and strengthening activities.
My Baby Isn't Talking
First words typically appear between 10 and 14 months, but there's enormous variation in what's normal. What matters most at first is whether your baby is communicating - pointing, gesturing, making eye contact, and babbling with different sounds - even if actual words haven't arrived yet.
Related Resources
Frequently asked questions
Is phelan-mcdermid syndrome (22q13 deletion) in babies normal?
When should I call the doctor about phelan-mcdermid syndrome (22q13 deletion) in babies?
When is phelan-mcdermid syndrome (22q13 deletion) in babies normal?
What causes phelan-mcdermid syndrome (22q13 deletion) in babies?
What should I mention to my pediatrician about phelan-mcdermid syndrome (22q13 deletion) in babies?
Is phelan-mcdermid syndrome (22q13 deletion) in babies normal at 0-6 months?
Is phelan-mcdermid syndrome (22q13 deletion) in babies normal at 6-18 months?
Should I go to the ER for phelan-mcdermid syndrome (22q13 deletion) in babies?
Does phelan-mcdermid syndrome (22q13 deletion) in babies go away on its own?
References
- [1]National Institutes of Health. Phelan-McDermid Syndrome. Genetic and Rare Diseases Information Center (GARD). NIH
- [2]National Organization for Rare Disorders. Phelan-McDermid Syndrome. NORD Rare Disease Database. NORD
- [3]Phelan-McDermid Syndrome Foundation. About PMS: Clinical Information and Family Resources. PMS Foundation
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Phelan-McDermid Syndrome (22q13 Deletion) in Babies.
Things to mention
- Describe when you first noticed phelan-mcdermid syndrome (22q13 deletion) in babies and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your child has significant speech delay, hypotonia, and autistic features and has not had chromosomal microarray testing.
- Mention if your child with PMS seems to have reduced pain perception and you need guidance on safety measures.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Your child has significant speech delay, hypotonia, and autistic features and has not had chromosomal microarray testing
- Your child with PMS seems to have reduced pain perception and you need guidance on safety measures
- Your child with PMS is persistently mouthing or chewing on objects and you need strategies for redirecting this behavior safely
Urgent signs to report immediately
- Your child with PMS has a seizure, staring spells, or episodes of unresponsiveness
- Your child with PMS is losing previously acquired skills (regression in speech, motor abilities, or self-care)
- Your child with PMS has injured themselves without showing a pain response and may have a significant injury (fracture, burn) that went unnoticed
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
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Related Resources
Bottom line
Most cases of phelan-mcdermid syndrome (22q13 deletion) in babies are normal. Talk to your pediatrician if your child with pms has a seizure, staring spells, or episodes of unresponsiveness.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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Related Medical Concerns
Early Signs of Autism in Babies and Toddlers
Autism spectrum disorder (ASD) can sometimes be identified as early as 12-18 months, though most children are not diagnosed until age 2-3. Early signs include limited eye contact, not responding to their name, lack of pointing or showing, limited social smiling, and absence of pretend play. Having one or two of these signs does not mean your child has autism - many typically developing children share individual traits. However, a pattern of multiple social communication differences warrants evaluation. Early intervention, regardless of eventual diagnosis, consistently leads to the best outcomes.
Low Muscle Tone (Hypotonia)
Low muscle tone means your baby's muscles feel less firm or their body feels "floppy" when you hold them. While it can sometimes indicate an underlying condition, many babies with mildly low tone do very well with support and strengthening activities.
My Baby Isn't Talking
First words typically appear between 10 and 14 months, but there's enormous variation in what's normal. What matters most at first is whether your baby is communicating - pointing, gesturing, making eye contact, and babbling with different sounds - even if actual words haven't arrived yet.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.
Achondroplasia (Dwarfism) in Babies
Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.
Adenoid Hypertrophy and Breathing
Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.