Atypical neurofibromatosis type 1 with unilateral limb hypertrophy mimicking overgrowth syndrome.

Neurofibromatosis type 1 (NF1; OMIM 162200), a dominantly inherited multitumor syndrome, results from mutations in the Neurofibromin 1 (NF1) gene. We present the case of a Hungarian woman with the clinical phenotype of NF1 over her whole body and the clinical features of unilateral overgrowth involving her entire left leg. This unusual phenotype suggested either the atypical form of NF1 or the coexistence of NF1 and overgrowth syndrome. Direct sequencing of the genomic DNA isolated from peripheral blood revealed a novel frameshift mutation (c.5727insT, p.V1909fsX1912) in the NF1 gene. Next-generation sequencing of 50 oncogenes and tumour suppressor genes, performed on the genomic DNAs isolated from tissue samples and peripheral blood, detected only wild-type sequences. Based on these results, we concluded that the patient is affected by an unusual phenotype of NF1, and that the observed unilateral overgrowth of the left leg might be a rare consequence of the identified c.5727insT mutation.

One mutation, two phenotypes: a single nonsense mutation of the CTSC gene causes two clinically distinct phenotypes.

BACKGROUND: Papillon-Lefévre syndrome (PLS; OMIM 245000) and Haim-Munk syndromes (HMS; OMIM 245010) are phenotypic variants of the same rare disease caused by mutations of the cathepsin C (CTSC) gene, and they exhibit autosomal recessive inheritance. AIMS: To identify diseases caused by mutations of the CTSC gene in two Hungarian patients and to perform haplotype analysis to elucidate any familial relationship between them. METHODS: Mutation screening and polymorphism analysis were performed by direct sequencing of the CTSC gene. RESULTS: Mutation screening of the CTSC gene from the two patients revealed the presence of the same homozygous nonsense mutation (c.748C/T; p.Arg250X). However, one patient exhibited the PLS phenotype and the other the HMS phenotype. Although these patients were not aware that they were related, haplotype analysis, especially the genotypes of the rs217116 and the rs217115 polymorphisms, clearly indicated that the patients carry the same haplotype, whereas the unrelated healthy controls carried several different haplotypes. CONCLUSIONS: Our results demonstrate that PLS and HMS are phenotypic variants of the same disease and, additionally, exclude the presence of a putative genetic modifier factor within the CTSC gene that is responsible for the development of the two phenotypes. We suggest that this putative genetic modifier factor is located outside the CTSC gene, or alternatively, that the development of the different phenotypes is the consequence of different environmental or lifestyle factors.