You just got a name for it.

DLL1 is a gene — a small instruction set inside every one of your child's cells. It tells brain cells when to grow, when to specialise, and what to become. When that instruction is partly missing or written incorrectly, brain development takes a different path. The detailed picture lives on the Understanding DLL1 page.

Every child with a DLL1 variant is different — even siblings can present differently. Common features include developmental delay, autism, seizures, low muscle tone, and brain MRI findings. Severity ranges widely, and many children make meaningful progress with the right supports.

About 40% of dominant DLL1 variants are 'de novo' — a brand-new change in your child that neither parent carries. About 60% are inherited from an affected parent who may have a milder version of the same condition. Knowing which applies to your family shapes the recurrence risk for future pregnancies.

Most families build a team: a developmental paediatrician, a neurologist if seizures are involved, occupational and speech therapy, school-based supports, and a genetic counsellor for the bigger-picture questions. Pacing matters — this is a marathon, not a sprint.

DLL1 is new enough that most teachers and many doctors will not have heard of it. A one-page summary you can hand over (we're building one) helps. Ask for an IEP or equivalent that names specific supports rather than the diagnosis.

Was DLL1 specifically reviewed in the genetic report? Is the variant classified as pathogenic, likely pathogenic, or VUS? What surveillance — MRI, EEG, spine imaging — makes sense for our child's specific findings? Is there a natural-history study or registry we can join?

You are not the first family on this road. The DLL1 community is small but growing on every continent. Reach out — even just to say hello.