Neurofibroma: Composed mainly of proliferating Schwann cells within their nerve sheath, neurofibromas can occur throughout the body, including the orbit and eyelid. Plexiform neurofibromas are associated with von Recklinghausen's disease and are infiltrative in nature. There are two types of NF that have been identified, both types are autosomal dominant and linked to chromosome 17. NF 1 is considered more common, occurring in 1:3,000 live births with patients exhibiting well recognized cutaneous cafe au late spots, neurofibromas, and Lisch iris nodules. The choroid may be thickened by the hamartomatous process and orbital bony malformations can occur, especially absence of the greater and lesser wing of the sphenoid creating a noticeable pulsating proptosis. Plexiform neurofibromas of the lateral upper eyelid can give the lid an S-configuration and clinically have the consistency of a "bag of worms". Lesions deep within the orbit as depicted above can cause proptosis, extraocular muscle disturbances and decreased vision due to optic nerve compression. NF 2 occurs in approximately 1:1,000,000 live births and consists of less prominent skin lesions and bilateral acoustic neuromas. Many of the other features above can also occur in this type of neurofibroma. Optic nerve gliomas are common in both types of neurofibromas. Back to Orbit