Neonatal Encephalopathy with Non-Epileptic Myoclonus
Autosomal dominant
This condition is caused by specific changes in one copy of KCNQ2 that increase the activity of a potassium channel in nerve cells (gain of function), unlike the more common KCNQ2 changes that reduce it and cause neonatal seizures. Reported changes have arisen de novo.
Signs and symptoms
From birth, babies have frequent startle-like muscle jerks (myoclonus) that do not show seizure activity on EEG, poor alertness, and breathing problems such as shallow or irregular breathing that may need support. Low body temperature has also been reported. Severe developmental delay follows, and some children later develop epileptic seizures.
What a diagnosis changes
Care is supportive, with breathing support when needed, careful neurological assessment to separate non-epileptic jerks from seizures, and developmental and therapy input. Reported cases have arisen de novo, but a parent can carry the change in only some of their cells, so genetic counselling and parental testing help clarify recurrence risk.
Genes analysed
