1
|
Malekkou A, Tomazou M, Mavrikiou G, Dionysiou M, Georgiou T, Papaevripidou I, Alexandrou A, Sismani C, Drousiotou A, Grafakou O, Petrou PP. A novel large intragenic DPYD deletion causing dihydropyrimidine dehydrogenase deficiency: a case report. BMC Med Genomics 2024; 17:78. [PMID: 38528593 PMCID: PMC10962175 DOI: 10.1186/s12920-024-01846-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 03/05/2024] [Indexed: 03/27/2024] Open
Abstract
BACKGROUND Dihydropyrimidine dehydrogenase (DPD), is the initial and rate-limiting enzyme in the catabolic pathway of pyrimidines. Deleterious variants in the DPYD gene cause DPD deficiency, a rare autosomal recessive disorder. The clinical spectrum of affected individuals is wide ranging from asymptomatic to severely affected patients presenting with intellectual disability, motor retardation, developmental delay and seizures. DPD is also important as the main enzyme in the catabolism of 5-fluorouracil (5-FU) which is extensively used as a chemotherapeutic agent. Even in the absence of clinical symptoms, individuals with either complete or partial DPD deficiency face a high risk of severe and even fatal fluoropyrimidine-associated toxicity. The identification of causative genetic variants in DPYD is therefore gaining increasing attention due to their potential use as predictive markers of fluoropyrimidine toxicity. METHODS A male infant patient displaying biochemical features of DPD deficiency was investigated by clinical exome sequencing. Bioinformatics tools were used for data analysis and results were confirmed by MLPA and Sanger sequencing. RESULTS A novel intragenic deletion of 71.2 kb in the DPYD gene was identified in homozygosity. The deletion, DPYD(NM_000110.4):c.850 + 23455_1128 + 8811del, eliminates exons 9 and 10 and may have resulted from a non-homologous end-joining event, as suggested by in silico analysis. CONCLUSIONS The study expands the spectrum of DPYD variants associated with DPD deficiency. Furthermore, it raises the concern that patients at risk for fluoropyrimidine toxicity due to DPYD deletions could be missed during pre-treatment genetic testing for the currently recommended single nucleotide polymorphisms.
Collapse
Affiliation(s)
- Anna Malekkou
- Biochemical Genetics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Marios Tomazou
- Bioinformatics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Gavriella Mavrikiou
- Biochemical Genetics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Maria Dionysiou
- Biochemical Genetics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Theodoros Georgiou
- Biochemical Genetics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Ioannis Papaevripidou
- Cytogenetics and Genomics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Angelos Alexandrou
- Cytogenetics and Genomics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Carolina Sismani
- Cytogenetics and Genomics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Anthi Drousiotou
- Biochemical Genetics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus
| | - Olga Grafakou
- Department of Pediatrics, Inborn Errors of Metabolism Clinic, Archbishop Makarios III Hospital, Korytsas 6, 2012, Nicosia, Cyprus
| | - Petros P Petrou
- Biochemical Genetics Department, The Cyprus Institute of Neurology and Genetics, P. O. Box 23462, 1683, Nicosia, Cyprus.
| |
Collapse
|
2
|
Hnoonual A, Plong-On O, Worachotekamjorn J, Charalsawadi C, Limprasert P. Clinical and molecular characteristics of FMR1 microdeletion in patient with fragile X syndrome and review of the literature. Clin Chim Acta 2024; 553:117728. [PMID: 38142803 DOI: 10.1016/j.cca.2023.117728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/09/2023] [Accepted: 12/16/2023] [Indexed: 12/26/2023]
Abstract
BACKGROUND Fragile X syndrome (FXS) is mainly caused by FMR1 CGG repeat expansions. Other types of mutations, particularly deletions, are also responsible for FXS phenotypes, however these mutations are often missed by routine clinical testing. MATERIALS AND METHODS Molecular diagnosis in cases of suspected FXS was a combination of PCR and Southern blot. Measurement of the FMRP protein level was useful for detecting potentially deleterious impact. RESULTS PCR analysis and Southern blot revealed a case with premutation and suspected deletion alleles. Sanger sequencing showed that the deletion involved 313 bp upstream of repeats and some parts of CGG repeat tract, leaving transcription start site. FMRP was detected in 5.5 % of blood lymphocytes. CONCLUSION According to our review of case reports, most patients carrying microdeletion and full mutation had typical features of FXS. To our knowledge, our case is the first to describe mosaicism of a premutation and microdeletion in the FMR1 gene. The patient was probably protected from the effects of the deletion by mosaicism with premutation allele, leading to milder phenotype. It is thus important to consider appropriate techniques for detecting FMR1 variants other than repeat expansions which cannot be detected by routine FXS diagnosis.
Collapse
Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Oradawan Plong-On
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | | | - Chariyawan Charalsawadi
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
| |
Collapse
|