Knowledge base · plain-language explainer

What is DEE? Understanding Developmental and Epileptic Encephalopathy.

DEE describes a group of serious brain conditions that affect both development and seizure activity, often from very early in life. For many families it's the overarching diagnosis their child receives before, or alongside, a more specific genetic diagnosis. SCN2A-related disorders are one of the most common known genetic causes of DEE, and the specialist core of our work.

The term

Breaking down what DEE means.

Developmental

The condition affects how the brain develops, delays in milestones, difficulties with learning, communication, or motor skills, or features of autism. In DEE, these are caused by the underlying brain condition itself, not only by seizures.

Epileptic

The condition involves epilepsy, recurring seizures from abnormal electrical activity in the brain. Seizures in DEE can be frequent, difficult to control, and varied in type.

Encephalopathy

A clinical term meaning a condition that affects brain function. In DEE, the encephalopathy refers to the global effect the condition has on the developing brain.

The term DEE replaced older terminology (such as "epileptic encephalopathy") to better reflect that the developmental impact is not caused solely by seizures, it is part of the condition itself.

Causes

What causes DEE?

In most cases, DEE has a genetic cause, a change (variant) in a specific gene that affects how the brain develops and functions. Over 100 different genes have now been linked to DEE, and new genetic causes continue to be identified through research.

Some of the more commonly identified genetic causes include:

SCN2A, the gene at the centre of SCN2A Australia's work
SCN1A (associated with Dravet syndrome)
KCNQ2
CDKL5
STXBP1
PCDH19
ARX
and many others

Not every person with DEE will have a confirmed genetic cause identified. As genetic testing technology improves, more families are receiving specific diagnoses, but for some, the cause remains unknown. In a smaller number of cases, DEE may be caused by structural brain abnormalities, metabolic conditions, or immune-mediated processes rather than a genetic variant.

Diagnosis

How is DEE diagnosed?

DEE is typically identified when a child (or, less commonly, an adult) presents with:

Seizures that begin in infancy or early childhood, often difficult to control
Developmental delays or regression
Evidence of encephalopathy on brain imaging or EEG

Diagnosis usually involves a combination of clinical assessment, electroencephalogram (EEG), brain imaging (MRI), and genetic testing. Genetic testing, through a gene panel, whole exome sequencing, or whole genome sequencing, is now recommended early in the diagnostic process for anyone presenting with DEE features.

For many families, the path to diagnosis is not straightforward. It may take multiple investigations, second opinions, and significant time before a specific genetic cause is identified. SCN2A Australia is here to help you navigate that process.

What it means

What does a DEE diagnosis mean for my family?

A DEE diagnosis, whether at the syndrome level or tied to a specific gene, is significant. It can bring both relief (finally having a name for what you are seeing) and grief (understanding the road ahead).

It does not define your family member's potential. People living with DEE conditions have rich, meaningful lives. The impact of a DEE condition varies enormously, and what is possible for any individual cannot be fully predicted at diagnosis.

What we know is that early support, coordinated care, connection with others who understand, and access to the latest research all make a genuine difference.

Where SCN2A fits

One specific cause within the broader DEE family.

SCN2A-related disorders are one specific cause within the broader DEE family. SCN2A Australia was founded by and for families affected by SCN2A, and that deep expertise remains central to everything we do.

Over time, our work has extended to support the broader DEE community, because the challenges families face, the advocacy work needed, and the research approaches being developed have much in common across genetic causes.

Whether your family member has an SCN2A variant, a diagnosis of another DEE-related condition, or is still awaiting a specific genetic result, SCN2A Australia can help.