Q: What is the likely diagnosis, and what is the underlying condition? show answer

A: Extensive optic pathway glioma in a child who most likely has neurofibromatosis type 1.

Q: When isolated to a shorter segment of optic nerve, what is the usual morphology? show answer

A: The optic nerve is variably enlarged, and the mass may either be fusiform or exophytic in appearance. Additionally the nerve may be elongated with kinking or buckling.

Q: What is the spectrum of behaviour of optic pathway gliomas in children with NF1. show answer

A: In patients with NF1 it is not unusual for these tumours to be quiescent, with little progression demonstrated over a number of years. In others, the tumours are more aggressive with extension along the optic pathways (as is the case in this patient).

Q: What is the genetic abnormality which results in NF1? show answer

A: Mutations of the NF1 gene locus is on chromosome 17q11.2 are responsible for neurofibromatosis type 1. The gene product of NF1 is neurofibromin, a protein which acts as a tumour suppressor; inactivation of the gene thus predisposes to tumour development.