Type 1 neurofibromatosis is an autosomal dominant hamartosis caused by mutations of the neurofibromin-1 gene. The classic features of the clinical phenotype include the presence of café-au-lait spots, neurofibromas, axillary and inguinal freckling, Lisch-nodules and deformities of the skeletal system, as well as the risk of developing multiple tumors, especially in the central nervous system. However, it is known from the literature that the phenotypic variability can pose a huge diagnostic difficulty. Aims: Our institute performs molecular genetic testing of the neurofibromin-1 gene since 2008; during this period several unusual phenotypic variants were found. Results, conclusion: The reported four cases represent interesting phenotypic variants or diagnostic challenges in which the final diagnosis was established by molecular genetic analysis.
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