Background: Evaluation of the pathogenicity of a gene variant of unknown significance
(VUS) is crucial for molecular diagnosis and genetic counseling, but can be challenging. This is especially
so in phenotypically variable diseases, such as von Hippel-Lindau disease (vHL). vHL is caused
by germline mutations in the VHL gene, which predispose to the development of multiple tumors such
as central nervous system hemangioblastomas and renal cell carcinoma (RCC).
Objective: We propose a method for the evaluation of VUS pathogenicity through our experience with
the VHL missense mutation c.241C>T (p.P81S).
Method: 1) Clinical evaluation of known variant carriers: We evaluated a family of five VHL p.P81S
carriers, as well as the clinical characteristics of all the p.P81S carriers reported in the literature; 2)
Evaluation of tumor tissue via genetic analysis, histology, and immunohistochemistry (IHC); 3) Assessment
of the variant’s impact on protein structure and function, using multiple databases, in silico algorithms,
and reports of functional studies.
Results: Only one family member had clinical signs of vHL with early-onset RCC. IHC analysis
showed no VHL protein expressed in the tumor, consistent with biallelic VHL inactivation. The majority
of in silico algorithms reported p.P81S as possibly pathogenic in relation to vHL or RCC, but there were
discrepancies. Functional studies suggest that p.P81S impairs the VHL protein’s function.
Conclusion: The VHL p.P81S mutation is most likely a low-penetrant pathogenic variant predisposing
to RCC development. We suggest the above-mentioned method for VUS evaluation with use of different
methods, especially a variety of in silico methods and tumor tissue analysis.