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.
OBJECTIVE
To explain the lack of genotype-phenotype correlation observed in a patient double heterozygous for the 852del22 and F508del mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.


METHODS
Case report.


METHODS
Medical laboratory department.


METHODS
A 42-year-old asymptomatic patient underwent genetic screening for in vitro fertilization (IVF).


METHODS
CFTR genetic screening (commercial kit aimed at detecting 57 mutations), segregation analysis, evaluation of the polymerase chain reaction (PCR) products using a denaturing high performance liquid chromatography (DHPLC), and sequence analysis.


METHODS
To avoid diagnostic errors and improve genetic counseling.


RESULTS
Segregation analysis allowed us to establish that the mutations were in trans. Analysis of the PCR products using a DHPLC apparatus showed a heteroduplex formation indicative of a heterozygous variant in exon 6A. Direct sequencing characterized the heterozygous variant as an A to T transversion at nucleotide position 875+11. Therefore, the change of one single nucleotide in a portion surrounding the 852del22 mutation facilitated the aspecific interaction between the commercial oligonucleotide probe and the amplified genomic DNA, which explains the 852del22 mutation false molecular positivity that was detected by the line probe assay.


CONCLUSIONS
The individualization of 852del22 mutation by a standard genetic panel should be confirmed by more extensive analyses.
Medical Laboratory Department, Genetics Section, Pordenone Hospital, Pordenone, Italy. gmiolo@libero.it
Gianmaria
G
Miolo
Marina
M
Crovatto
Massimo
M
Manno
Barbara
B
Pivetta
Giovanni
G
Tessitori
Luigi
L
Picci
D000328:Adult; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D005189:False Positive Reactions; D005307:Fertilization in Vitro; D017353:Gene Deletion; D005820:Genetic Testing / Q000592:standards*; D014644:Genetic Variation; D006579:Heterozygote; D006801:Humans; D007248:Infertility, Male / Q000235:genetics*; D008297:Male; D015203:Reproducibility of Results
C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator