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Klinische Padiatrie

Constitutional mismatch repair-deficiency and whole-exome sequencing as the means of the rapid detection of the causative MSH6 defect.


PMID 25431869

Abstract

Cases of children with more than one type of cancer either diagnosed simultaneously or successively, rarely occur in pediatric oncology. A second malignant neoplasm may be caused by mutagenic effects of the treatment of the primary malignancy and/or may point towards an underlying genetic cancer susceptibility syndrome. One example of such a syndrome is constitutional mismatch repair-deficiency, (CMMR-D) which carries an increased risk of various tumors including childhood hematologic malignancies and Lynch syndrome associated tumors. Timely diagnosis of CMMR-D is crucial, since this diagnosis has implications for the entire family. We report the case of a 15-year-old girl who was born to consanguineous parents. At the age of 20 months she was diagnosed with a T-cell non-Hodgkin lymphoma. Treatment was given according to NHL-BFM 95. 12 years later, an invasive adenocarcinoma of the colon was surgically removed which relapsed shortly afterwards. Whole-exome sequencing of germline DNA was employed to rapidly detect the underlying mutation in this suspected CMMR-D patient. After a short turnaround time of less than 3 weeks, the diagnosis of CMMR-D could be confirmed by the identification of a homozygous 29-bp deletion in MSH6 (exon 6), which was confirmed by independent methods. We demonstrate that "bed-side" whole-exome sequencing is both feasible and cost-effective and may be the method of choice to rapidly uncover the genetical basis of (inherited) diseases.