What is the prevalence of 22q13 deletion / Phelan-McDermid Syndrome?

TL;DR: Phelan-McDermid syndrome (22q13 deletion) is a rare genetic condition with an estimated prevalence between 1 in 8,000 and 1 in 15,000 individuals, though these figures are likely underestimated due to historical challenges in diagnostic testing. While the exact global incidence remains difficult to track precisely, the syndrome is increasingly recognized as a significant cause of global developmental delay and autism spectrum disorder.

Is 22q13 deletion / Phelan-McDermid syndrome considered rare or ultra-rare?

Phelan-McDermid syndrome, often referred to as 22q13 deletion syndrome, is classified as a rare genetic disorder. Because the clinical presentation can be broad—ranging from mild to profound developmental delays—many individuals remain undiagnosed or are misdiagnosed with non-specific intellectual disabilities. Current clinical literature suggests the prevalence is likely higher than initial estimates, as improved access to chromosomal microarray (CMA) testing has significantly increased the number of identified cases globally.

What do we know about the demographics and distribution of Phelan-McDermid syndrome?

Research indicates that 22q13 deletion syndrome affects males and females with equal frequency, suggesting no clear gender-based biological predisposition. Regarding age of onset, the condition is congenital, meaning the genetic change is present from birth; however, clinical diagnosis often occurs in early childhood when developmental milestones are missed. There is currently no evidence to suggest that 22q13 deletion syndrome is linked to specific ethnic groups or geographic regions, as it has been identified in diverse populations worldwide.

What are the primary challenges in determining the true prevalence of this condition?

Accurately mapping the prevalence of 22q13 deletion syndrome is complicated by several factors that often lead to under-reporting in medical databases:

• Diagnostic Limitations: Prior to the widespread adoption of chromosomal microarrays, many deletions were too small to be detected by standard karyotyping.


• Phenotypic Variability: The severity of symptoms varies greatly depending on the size and location of the deletion on the 22q13 chromosome, leading some individuals to remain undiagnosed if their symptoms are mild.


• Lack of Universal Screening: There is no standardized global newborn screening for Phelan-McDermid syndrome, meaning cases are only identified once symptoms become clinically apparent.

How does the DiseaseMaps.org community contribute to our understanding?

While clinical databases provide formal epidemiological data, real-world experience is vital for understanding the lived reality of rare disease. Currently, 35 people with 22q13 deletion / Phelan-McDermid syndrome have joined the DiseaseMaps.org community and shared their experiences. This community-driven data complements clinical statistics by highlighting the diagnostic journey and the diverse ways in which Phelan-McDermid syndrome impacts daily life, providing a platform for families to connect and share localized insights that are not always captured in traditional medical literature.

Next steps

• Consult with a clinical geneticist to discuss genetic testing options, such as chromosomal microarray analysis, if you suspect a diagnosis of 22q13 deletion syndrome.


• Connect with the Phelan-McDermid Syndrome Foundation to access resources, clinical trial information, and family support networks.


• Join the DiseaseMaps.org community to share your experience and learn from the collective journey of other families affected by Phelan-McDermid syndrome.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.

References

• Orphanet: Phelan-McDermid syndrome (ORPHA:32428).


• NIH Genetic and Rare Diseases Information Center (GARD): 22q13 deletion syndrome.


• OMIM (Online Mendelian Inheritance in Man): #606232 Phelan-McDermid Syndrome.


• Phelan-McDermid Syndrome Foundation: Patient registry and medical research summaries.