1st March 2024

A 16-year-old female presents to the genetic clinic with severe learning difficulties

A 16-year-old female presents to the genetic clinic with severe learning difficulties. Her mother noted that her pregnancy and birth were largely unremarkable. The patient’s development during childhood was significantly delayed in motor and speech functions, and she only began walking at three years old. Her communication skills remain primarily limited towards simple words and phrases.

She is easily amused, occasionally laughs inappropriately with minimal stimulus, and appears to have an apparent happy demeanour often. Her mother also notes that she has had seizures since childhood, but this has been controlled with levetiracetam.

Given the likely underlying diagnosis, which of the following genetic mechanisms has resulted in the clinical presentation?

Select the SINGLE most appropriate option from the list below. Select ONE option only.