PathWays Case Study: July 18
A 34-year-old, asymptomatic pregnant female was referred for genetic testing due to a previously positive carrier screen for Gaucher disease (GD). According to her outside test report, two pathogenic variants (D448H and L483P) were detected, and the results were stated to be consistent with GD affected.
Follow-up biochemical genetic testing was performed on peripheral leukocytes. The results (7.5 nmol/h/m) were slightly lower than reference range (>8.7 nmol/h/m), but this was not sufficient to resolve whether the patient was a carrier of or affected with GD. Thus, molecular testing was ordered to confirm the presence and to further determine the phase of the two mutations.
Peripheral blood samples from the proband and her mother were received for GBA full gene analysis by Sanger sequencing following a long range polymerase chaing reaction (LR-PCR). Sequencing results were negative for any known mutations in both the patient and her mother. The patient appeared to be homozygous for the wild-type allele, including all SNPs detected in exon 9 and deep into the flanking intronic regions. Gel electrophoresis of the PCR product demonstrated an approximately ˜50% reduction in the amount of DNA in the patient's sample as compared to her mother and controls.
Yang Cao, Ph.D.
Resident, Clincal Molecular Genetics
Linda Hasadsri, M.D., Ph.D.
Senior Associate Consultant, Laboratory Genetics and Genomics