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Lisch Nodules

 Lisch nodules are melanocytic hamartomas, usually clear yellow to brown, that appear as well defined, dome shaped elevations projecting from the surface of the iris. They may be seen without magnification but a slit lamp examination may be necessary to distinguish them from naevi on the iris which present as flat or minimally elevated, densely pigmented lesions with blurred margins. The nodules are thought not to cause any ophthalmologic complication.

Lisch nodules are the most common clinical finding in adults over 20 years of age with type I neurofibromatosis (NF-1). Unlike cafe au lait spots, multiple nodules are specific for peripheral neurofibromatosis - Von Recklinghausen disease. They may occur in segmental neurofibromatosis which is due to a somatic mutation of the NF-1 gene but are generally absent in central neurofibromatosis. In children, nodules are a more likely finding than neurofibromas. This is an example of an ocular manifestation of a genetic disease. NF-1 has been mapped to a gene defect in chromosome 17.

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