The study found variations in the FBXW7 gene were associated with the newly identified condition, which causes mild to severe developmental delay, intellectual disability, hypotonia and gastrointestinal issues.

Murdoch Children’s researcher Dr Sarah Stephenson said because the FBXW7 gene regulated the life-cycle of cells, cell growth and survival, the research team speculated that abnormal cell proliferation during brain development may underpin the broad spectrum of brain abnormalities identified in this new disorder.

“FBXW7 now joins a steeply increasing number of intellectual disability/autism spectrum disorder genes that have been implicated in disorders that affect nervous system development, leading to atypical brain function, affecting emotion, learning ability, self-control and memory,” she said.

Almost all affected people had developmental delay and intellectual disability, ranging from borderline to severe, 62% had decreased muscle tone, 46% noted feeding difficulties and constipation and 23% had seizures.

Brain imaging also detailed variable underlying structural differences affecting the cerebellum, nerve fibres and white matter.

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