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Diagnosis of mendelian disorders and clinical whole-exome sequencing


Whole-exome sequencing is a diagnostic approach for the identification of molecular defects in patients with suspected genetic disorders.

Researchers have developed technical, bioinformatic, interpretive, and validation pipelines for whole-exome sequencing in a certified clinical laboratory to identify sequence variants underlying disease phenotypes in patients.

Data on the first 250 probands for whom referring physicians ordered whole-exome sequencing were presented.

Patients had a range of phenotypes suggesting potential genetic causes. Approximately 80% were children with neurologic phenotypes.

Researchers have identified 86 mutated alleles that were highly likely to be causative in 62 of the 250 patients, achieving a 25% molecular diagnostic rate.

Among the 62 patients, 33 had autosomal dominant disease, 16 had autosomal recessive disease, and 9 had X-linked disease.

A total of 4 probands received two nonoverlapping molecular diagnoses, which potentially challenged the clinical diagnosis that had been made on the basis of history and physical examination.

A total of 83% of the autosomal dominant mutant alleles and 40% of the X-linked mutant alleles occurred de novo.

Recurrent clinical phenotypes occurred in patients with mutations that were highly likely to be causative in the same genes and in different genes responsible for genetically heterogeneous disorders.

In conclusion, whole-exome sequencing identified the underlying genetic defect in 25% of consecutive patients referred for evaluation of a possible genetic condition. ( Xagena )

Yang Y et al, N Engl J Med 2013; 369: 1502-1511

XagenaMedicine_2013



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