Heterozygous variant at nucleotide position 875+11A>T in exon 6A cystic fibrosis transmembrane conductance regulator gene induces 852del22 mutation false-positivity by line probe assay

The first case report of double homozygous of 2 different mutations in the CFTR gene in Saudi Arabia

The first cases of a rare double homozygosity of two different mutations in the cystic fibrosis trans-regulator gene (CFTR) of a cystic fibrosis patient in Saudi Arabia. Details of the family screening and a review of the literature on similar cases are discussed.

Genetic screening for von Hippel-Lindau gene mutations in non-syndromic pheochromocytoma: low prevalence and false-positives or misdiagnosis indicate a need for caution

Genetic testing of tumor susceptibility genes is now recommended in most patients with pheochromocytoma or paraganglioma (PPGL), even in the absence of a syndromic presentation. Once a mutation is diagnosed there is rarely follow-up validation to assess the possibility of misdiagnosis. This study prospectively examined the prevalence of von Hippel-Lindau (VHL) gene mutations among 182 patients with non-syndromic PPGLs. Follow-up in positive cases included comparisons of biochemical and tumor gene expression data in 64 established VHL patients, with confirmatory genetic testing in cases with an atypical presentation. VHL mutations were detected by certified laboratory testing in 3 of the 182 patients with non-syndromic PPGLs. Two of the 3 had an unusual presentation of diffuse peritoneal metastases and substantial increases in plasma metanephrine, the metabolite of epinephrine. Tumor gene expression profiles in these 2 patients also differed markedly from those associated with established VHL syndrome. One patient was diagnosed with a partial deletion by Southern blot analysis and the other with a splice site mutation. Quantitative polymerase chain reaction, multiplex ligation-dependent probe amplification, and comparative genomic hybridization failed to confirm the partial deletion indicated by certified laboratory testing. Analysis of tumor DNA in the other patient with a splice site alteration indicated no loss of heterozygosity or second hit point mutation. In conclusion, VHL germline mutations represent a minor cause of non-syndromic PPGLs and misdiagnoses can occur. Caution should therefore be exercised in interpreting positive genetic test results as the cause of disease in patients with non-syndromic PPGLs.