Rapid development of optic glioma in a patient with hybrid phakomatosis: neurofibromatosis type 1 and tuberous sclerosis.

Increased propensity for tumor formation in neurofibromatosis and tuberous sclerosis exists because of defective tumor-suppressor genes. Although different tumor-suppressor genes may be involved in neurofibromatosis and tuberous sclerosis, at the cellular level these genes share rather common enzymatic pathways. We believe these genetic malfunctions have resulted in a cumulative or additive effect for rapid growth of optic glioma in the following unusual case that has hybrid phakomatosis.