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

TL;DR: Phelan-McDermid Syndrome, also known as 22q13 deletion syndrome, was first clinically described in 1985 by Dr. Katy Phelan and Dr. Heather McDermid. Since its discovery, medical understanding of the condition has evolved from simple cytogenetic observations to a sophisticated grasp of the SHANK3 gene's critical role in neurological development.

When was Phelan-McDermid Syndrome first identified?

The medical history of Phelan-McDermid Syndrome began in the mid-1980s. In 1985, Dr. Katy Phelan, a cytogeneticist, identified a series of patients who shared a common deletion at the terminal end of the long arm of chromosome 22 (22q13). Shortly thereafter, Dr. Heather McDermid contributed significantly by mapping the molecular details of these deletions. Initially, the condition was described primarily through its physical manifestations, such as hypotonia and delayed speech, before the specific genetic mechanisms were fully elucidated.

How has our understanding of 22q13 deletion evolved?

Early researchers initially struggled to define the syndrome because the deletions varied in size, leading to a wide spectrum of clinical presentations. A major milestone occurred in the early 2000s when the SHANK3 gene—located within the 22q13 region—was identified as the primary driver of the neurological symptoms associated with Phelan-McDermid Syndrome. This shifted the medical perspective from viewing the condition as a generic chromosomal loss to a specific "synaptopathy," or a disorder of the synapses, which provided a clearer target for future therapeutic research.

What were the historical misconceptions about the syndrome?

In the early years of diagnosis, many individuals with Phelan-McDermid Syndrome were misdiagnosed with non-specific developmental delays or autism spectrum disorder without a known genetic cause. Because the deletion is often too small to be detected by standard karyotyping, many families spent years in a "diagnostic odyssey." The introduction of chromosomal microarray (CMA) technology in the late 2000s corrected these misconceptions, allowing clinicians to accurately identify the 22q13 deletion where traditional testing had previously failed.

How have technology and patient advocacy transformed care?

The evolution of patient advocacy has been instrumental in the progress of Phelan-McDermid Syndrome research. Organizations like the Phelan-McDermid Syndrome Foundation (PMSF) have unified families, creating a robust patient registry that helps researchers understand the natural history of the disease. Modern genetic sequencing has allowed for a much more nuanced understanding of genotype-phenotype correlations, ensuring that families receive more accurate prognostic information than was possible in the 1990s.

• 1985: First clinical reports of terminal 22q13 deletions published.


• 2001: The SHANK3 gene is implicated as the major gene responsible for the neurological features of Phelan-McDermid Syndrome.


• 2008: Widespread adoption of microarray technology significantly increases the diagnostic rate for 22q13 deletions.


• Community Impact: Currently, 35 people with Phelan-McDermid Syndrome are connected through the DiseaseMaps.org platform, sharing lived experiences that supplement clinical data.

Next steps

• Consult a clinical geneticist to review the specific size and location of the 22q13 deletion.


• Join the Phelan-McDermid Syndrome Foundation to access the latest clinical trial information and family support resources.


• Connect with the community on DiseaseMaps.org to share experiences with other families navigating the same diagnosis.

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

References

• NIH GARD: Phelan-McDermid Syndrome Overview.


• Orphanet: 22q13.3 deletion syndrome (ORPHA:285).


• OMIM: Phelan-McDermid Syndrome (Entry #606232).


• Phelan-McDermid Syndrome Foundation (PMSF): Historical archives and research publications.