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Lisch nodule, also known as iris hamartoma, is a pigmented hamartomatous nodular aggregate of dendritic melanocytes affecting the iris,<ref name=robbins7>Template:Citation</ref> named after Austrian ophthalmologist Karl Lisch (1907–1999), who first recognized them in 1937.<ref name=Lukacs1997>Template:Citation</ref>
The first published use of the term Lisch nodule was in the New England Journal of Medicine "Medical Progress" series article of December 31, 1981 (Riccardi VM: Von Recklinghausen Neurofibromatosis. N Engl J Med 1981;305:1617–27).
These nodules are found in neurofibromatosis type 1, and are present in greater than 94% of patients over the age of six.<ref name=robbins7 /> They are clear, yellow-brown,<ref name=Richetta2004>Template:Citation</ref> oval to round, dome-shaped papules that project from the surface of the iris. These nodules typically do not affect vision, but are very useful in diagnosis.<ref name=robbins7 /> They are detected by slit lamp examination.<ref name=Richetta2004 /> Immunohistochemistry stains positive against the proteins vimentin and S-100, and points to an ectodermal origin for the nodules.<ref name=Lukacs1997/> Their precise origin and structure, however, are still under investigation.<ref name=Richetta2004 /> They can rarely be seen in neurofibromatosis type 2.<ref>Template:Cite journal</ref>