Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations...

Area of Science:

• Genetics
• Oncology
• Medical Genetics

Background:

• Neurofibromatosis type 1 (NF1) presents with highly variable clinical features.
• Previous genotype-phenotype correlations for NF1 missense mutations were limited to specific sites (p.Arg1809, p.Met922del), associated with mild phenotypes.
• A significant portion of NF1 patients lack clear genotype-phenotype correlations for predicting disease severity.

Purpose of the Study:

• To investigate the clinical significance of constitutional missense mutations in the NF1 gene at codons 844-848.
• To establish a genotype-phenotype correlation for this specific region within the NF1 gene.
• To assess the risk of specific NF1-associated complications, including tumors and malignancies, in individuals with these mutations.

Main Methods:

• Analysis of 162 individuals (129 unrelated probands, 33 relatives) with constitutional missense mutations in NF1 codons Leu844, Cys845, Ala846, Leu847, and Gly848.
• Comparison of clinical features, including tumor prevalence and malignancy risk, with classic NF1 cohorts.
• Statistical analysis to determine the significance of observed correlations (p < 0.0001, p = 0.0061).

Main Results:

• Recurrent missense mutations in NF1 codons 844-848 were identified in approximately 0.8% of unrelated NF1 mutation-positive probands.
• Individuals with these mutations showed significantly higher prevalence of major superficial plexiform neurofibromas and symptomatic spinal neurofibromas.
• Nearly half of the individuals experienced optic pathway gliomas and/or skeletal abnormalities; a notable predisposition to malignancies was observed compared to the general NF1 population.

Conclusions:

• Missense mutations in the NF1 region 844-848 are associated with a severe NF1 phenotype, including increased risks of specific tumors and malignancies.
• A distinct genotype-phenotype correlation exists for NF1 mutations in this cysteine-serine-rich domain (CSRD).
• These findings are crucial for improving genetic counseling and clinical management strategies for affected individuals.