Clinical Reference Hub

SCN1A Mechanistic Divergence

Providing diagnostic clarity, pharmacological guidance, and published literature regarding the ~11% of SCN1A patients presenting with Gain-of-Function mutations.

Loss of Function (LoF)

~89% of Cases (Dravet Phenotype)

Mechanism: Haploinsufficiency. The NaV1.1 sodium channel is broken, truncated, or locked closed, leading to inadequate inhibition.
Onset: Typically presents around 6 months of age.
Pharmacology: Sodium Channel Blockers (SCBs) are strictly contraindicated as they further reduce already deficient channel function.

Gain of Function (GoF)

~11% of Cases (EIDEE Phenotype)

Mechanism: Overactivity. The NaV1.1 channel exhibits delayed inactivation or is "stuck open," resulting in a massive influx of sodium.
Onset: Frequently presents much earlier (0-3 months) as severe neonatal encephalopathy.
Pharmacology: Sodium Channel Blockers (SCBs) are often strongly indicated to close the overactive channels and suppress excitability.

The Pharmacological Treatment Paradox

Because SCN1A has historically been synonymous with Dravet Syndrome in broad clinical settings, newly diagnosed neonates with GoF mutations are at extreme risk of iatrogenic harm.

Placing a GoF infant on a standard Dravet protocol prevents them from receiving Sodium Channel Blockers (e.g., Oxcarbazepine, Phenytoin)—the exact pharmacological agents required to counteract the p.Thr226Met mechanism. Rapid Whole Exome Sequencing (rWES) and mechanical differentiation are critical to prevent prolonged status epilepticus.