Clinical and genetic significance of unilateral Lisch nodules.

Bilateral Lisch nodules are highly characteristic for neurofibromatosis type 1 (NF1). We wished to study the clinical and genetic implications of unilateral Lisch nodules. Retrospective study of the clinical data of 59 patients who received genetic counselling for neurofibromatosis type 1 (NF1) or type 2 (NF2) and were examined at the department of ophthalmology. Unilateral Lisch nodules were observed in 4 cases: one child with NF1 initially presented unilateral Lisch nodules but developed bilateral Lisch nodules by the age of 9. In 2 cases segmental NF1 was the most probable diagnosis and in one case isolated Lisch nodules were observed. Of the 35 NF1 patients 28 ultimately developed bilateral Lisch nodules. Seven NF1 patients did not demonstrate the nodules. At follow-up no Lisch nodules were detected in 2 neurofibromatosis type 2 patients, in 4 patients in whom the diagnosis of NF1 remained doubtful and in 15 patients without NF1. Because isolated Lisch nodules are very rare, their presence warrants a thorough patient history and clinical examination to either confirm or exclude generalised or segmental neurofibromatosis type 1.