As the mother, could I be a carrier of a 22q11.2 microdeletion given my attention‑deficit/hyperactivity disorder (ADHD), normal intelligence, no health problems, and a non‑vision‑impairing coloboma?

Yes, you could be a carrier of a 22q11.2 microdeletion

Your clinical presentation—ADHD, normal intelligence, and coloboma without vision impairment—is entirely consistent with being a mildly affected carrier of a 22q11.2 deletion, and parental genetic testing should be performed immediately if your child has been diagnosed with this syndrome.

Why Your Features Suggest Carrier Status

The 22q11.2 deletion syndrome exhibits extreme phenotypic variability, and approximately 10% of cases are inherited rather than de novo 1. Critically, when the deletion is inherited, affected offspring typically show more severe manifestations than their carrier parent, with expectations for lower IQ in inherited cases 1. Your profile fits this pattern perfectly:

Your Specific Features Align with Mild 22q11.2DS:

• ADHD: This is one of the most common neurodevelopmental features in 22q11.2 deletion carriers, reported in 40-50% of affected individuals 2, 3

• Normal intelligence: While most individuals with 22q11.2DS have borderline IQ (70-85), there is substantial variability, and some carriers fall into the low-average to normal intelligence range 1. Parents who are carriers typically have milder cognitive effects than their affected children

• Coloboma: Ocular abnormalities, including coloboma, are recognized features of the 22q11.2 deletion spectrum 4

• No other health problems: Many carriers are minimally symptomatic or have such mild features that the diagnosis is only made after their more severely affected child is identified 5

The Critical Genetic Mechanism

The 22q11.2 deletion typically occurs through non-allelic homologous recombination between low copy repeats during meiosis 5, 6. When inherited:

• The carrier parent often has a milder phenotype
• The affected child experiences a 30-point IQ deficit relative to parental IQ on average 1
• Additional genetic modifiers and environmental factors contribute to the more severe presentation in offspring 5

What You Must Do Now

According to 2023 guidelines, parental genetic testing using FISH, MLPA, or chromosomal microarray is recommended at initial diagnosis/assessment 1. This testing should be performed on you specifically because:

1. Your ADHD and coloboma are recognized features of 22q11.2DS
2. Identifying carrier status has immediate implications for:
   • Genetic counseling for future pregnancies
   • Your own medical surveillance (increased risks for psychiatric disorders, Parkinson disease, cardiovascular issues, and metabolic conditions as you age) 1
   • Family planning and reproductive counseling 1

Important Caveats

• Even if you test positive as a carrier, your relatively mild presentation does not predict the severity in future children—there is marked variability
• If you test negative, your child's deletion would be de novo (90% of cases) 2
• Smaller, atypical deletions in the 22q11.2 region can produce variable phenotypes and may be harder to detect with older testing methods 3

The bottom line: Request genetic testing immediately through FISH, MLPA, or chromosomal microarray to definitively determine your carrier status 1.