Deficient DNA mismatch repair and persistence of SARS-CoV-2 RNA shedding: a case report of hereditary nonpolyposis colorectal cancer with COVID-19 infection

Background Several independent risk factors have been reported to influence viral shedding following COVID-19 infection, but the influence of host-related molecular factors has not yet been described. We report a case of a cancer patient with Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC) who manifested SARS-CoV-2 PCR (polymerase chain reaction) positivity for at least 54 days after contracting mild COVID-19 illness. We propose that deficient mismatch repair (MMR) may play a role in the prolonged SARS-CoV-2 RNA shedding. Case presentation A patient with Lynch syndrome was under surveillance for metastatic adenocarcinoma after completing palliative chemotherapy in October 2019. Between the period of April 2020 to June 2020, he was admitted multiple times to address several clinical needs mainly related to his underlying malignancy. These included progressive disease observed in the aortocaval lymph nodes leading to recurrent episodes of upper gastrointestinal bleeding, dehydration resulting in acute kidney injury and a short-lived episode of pyrexia. A SARS-CoV-2 PCR of the nasopharyngeal swab (NPS) was positive at his initial admission with mild COVID-19 symptoms. He remained positive on subsequent admissions when tested routinely for SARS-CoV-2 without demonstrating any apparent clinical features of COVID-19 infection. The MMR pathway, a component of DNA damage response (DDR), is impaired in Lynch syndrome due to an inherited genetic mutation. This pathway is also required for viral clearance from the host cells following certain RNA viral infections like influenza virus and other coronaviridae. Here we provide a current understanding of the importance of DDR deficiencies in the clearance of RNA virus and suggest how this may play a similar role in the clearance of COVID-19, as evident in our case that demonstrated persistent positivity. Conclusion The importance of understanding the scientific basis of extended viral shedding during the COVID-19 pandemic is now centre-stage in the establishment of robust track and trace services to allow the recovery and function of societies and economies. This patient with Lynch syndrome recovered from infection but had prolonged viral positivity, which might merit further investigation to better understand the effect of this condition on infection duration and outcome.

Hereditary Nonpolyposis Colorectal Cancer (HNPCC)/Lynch Syndrome: Surveillance and Diagnostic strategies

Introduction: Hereditary nonpolyposis colorectal cancer (HNPCC, Lynch syndrome) is an autosomal dominant genetic disease. The disease is caused by a mutation in one of four genes of the DNA mismatch repair system and increases the risk for various cancers, especially the uterine and colon cancers. The prevalence of this disease in the general population is about 1 in 500 and it causes about 2-3% of colorectal cancers. Lynch syndrome is diagnosed in two stages: 1) the person is suspected of having the disease (because a patient is unusually diagnosed with cancer at a young age), and 2) evidence of incomplete repair defect is seen in the tumor tissue (microsatellite instability). The detection of a pathogenic mutation confirms the diagnosis in these patients and enables predictive testing for other family members. Diagnostic evaluation of Lynch syndrome should be performed with appropriate genetic counseling. Systemic colonoscopy surveillance could identify colon cancers at an earlier stage before patients present clinical symptoms. Conclusion: Although many studies have been done, but the benefits of an individualized, risk-adapted surveillance strategy are still unclear. Until this is identified, Lynch syndrome patients and healthy carriers with causative mutations should be monitored by annual colonoscopy and annual gynecological examination (for women).

MLH1 and MSH2 Gene Mutations and Polymorphisms in Six Malay Families with Hereditary Nonpolyposis Colorectal Cancer

Background: Hereditary nonpolyposis colorectal cancer (HNPCC) also known as Lynch syndrome is commonly caused by genetic alterations in any of the four mismatch repair (MMR) genes; MLH1, MSH2, MSH6 and PMS2. This is the first study aimed to investigate genetic variants in Malay HNPCC families. Methods: Six Malay HNPCC families who fulfilled any of the Bethesda criteria were recruited into this study. A total of 3 ml of blood was withdrawn from each patient in the families. The samples were further analyzed using polymerase chain reaction and direct sequencing of the selected exons of MLH1 and MSH2 genes. Results: Two missense mutations and four single nucleotide polymorphisms (SNPs) were identified in six patients. These variants in the MLH1 and MSH2 genes were identified in four families who met the revised Bethesda guidelines. In two families, no mutation and polymorphism was identified in both the exon and intron of the respective genes. Of the mutations and polymorphisms identified, five have never been reported in Malay HNPCC families before. A missense mutation was detected in exon 5 of the MLH1 gene, c.394G>C (p.Asp132His) and four mutations and polymorphisms were detected in the MSH2 gene; heterozygous c.211+98T>C and c.211+9C>G and homozygous c.211+98T>C and c.211+9C>G, c.367-86A>C and c.382C>G. Conclusion: The results represented a new spectrum of mutations and polymorphisms in the Malay HNPCC families. However, a larger study involving additional families and analysis is required to determine the impact and nature of the identified mutations and polymorphisms.

Deficient DNA mismatch repair and persistence of SARS-CoV-2 RNA shedding: A case report of Hereditary Nonpolyposis Colorectal Cancer with COVID-19 infection.

Background:Several independent risk factors have been reported to influence viral shedding following COVID-19 infection, but host related molecular factors have not been described yet. We report a case of a cancer patient with Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC) who manifested SARS-COV-2 PCR (polymerase chain reaction) positivity for at least 54 days after contracting mild COVID-19 illness and propose that deficient mismatch repair (MMR) may have a role in the prolonged SARS-CoV-2 RNA shedding.Case Presentation:A patient with Lynch syndrome was on surveillance for metastatic adenocarcinoma after completion of palliative chemotherapy in October 2019. Between the period of April 2020 to June 2020, he required multiple admissions addressing several clinical needs mainly related to his underlying malignancy. These included progressive disease in the interaortocaval lymph nodes leading to recurrent episodes of upper gastrointestinal bleeding, dehydration resulting in acute kidney injury and a short-lived episode of pyrexia. A SARS-COV-2 PCR of the nasopharyngeal swab (NPS) was positive at his initial admission with mild COVID-19 symptoms. He remained positive on subsequent admissions when tested routinely for SARS-COV-2 without demonstrating any obvious clinical features of COVID-19 infection.The MMR pathway, a component of DNA damage response (DDR), is impaired in Lynch syndrome due to an inherited genetic mutation. This pathway is also required for viral clearance from the host cells following certain RNA viral infections like influenza virus and other coronaviridae. Here we provide current understanding of the importance of DDR deficiencies in the clearance of RNA virus and suggest how this may play a similar role in the clearance of COVID-19 as evident in our case that demonstrated persistent positivity.Conclusion:The importance of understanding the scientific basis of extended viral shedding during the COVID-19 pandemic is now centre-stage in the establishment of robust track and trace services to allow the recovery and function of societies and economies. We propose that deficient-MMR may contribute to the persistence of SARS-CoV-2 RNA shedding. Future studies could open new avenues for research and may give rise to epidemiological or early therapeutic interventions.

Dominantly Inherited Hereditary Nonpolyposis Colorectal Cancer Not Caused by MMR Genes

In the past two decades, multiple studies have been undertaken to elucidate the genetic cause of the predisposition to mismatch repair (MMR)-proficient nonpolyposis colorectal cancer (CRC). Here, we present the proposed candidate genes according to their involvement in specific pathways considered relevant in hereditary CRC and/or colorectal carcinogenesis. To date, only pathogenic variants in RPS20 may be convincedly linked to hereditary CRC. Nevertheless, accumulated evidence supports the involvement in the CRC predisposition of other genes, including MRE11, BARD1, POT1, BUB1B, POLE2, BRF1, IL12RB1, PTPN12, or the epigenetic alteration of PTPRJ. The contribution of the identified candidate genes to familial/early onset MMR-proficient nonpolyposis CRC, if any, is extremely small, suggesting that other factors, such as the accumulation of low risk CRC alleles, shared environmental exposures, and/or gene–environmental interactions, may explain the missing heritability in CRC.