[Lisch nodules. Markers of neurofibromatosis 1 and immunohistochemical references for neuroectodermal...

Iris nodules in neurofibromatosis I have become an important tool in the differential diagnosis of phakomatoses. The clinical appearance and importance of these nodules first recognized by Karl Lisch in Munich in 1937. The diagnosis and differential diagnosis of Lisch nodules are illustrated. The importance of iris nodules in genetic counselling of patients and their relatives is discussed, with emphasis on monosymptomatic cases. Histologically Lisch nodules are formed by aggregations of oval to round cells that form dome-shaped papules on the anterior layer of the iris. Immunohistochemically these cells are characterized by positive staining with antibodies against vimentin and S-100 protein. This proves their ectodermal differentiation. Thus Lisch nodules can be seen as a direct manifestation of neuroectodermal disturbances in neurofibromatosis I.