PTEN hamartoma tumour syndrome: case report based on data from the Iranian hereditary colorectal cancer registry and literature review

Germline variants in patients from the Iranian hereditary colorectal cancer registry

BACKGROUND AND AIM

Hereditary cancer syndromes account for 6-10% of all colorectal cancer (CRC) cases and 20% of early-onset CRC. Identifying novel pathogenic germline variants can impact genetic testing, counseling, and surveillance. This study aimed to determine the prevalence of germline variants associated with hereditary CRC in the Iranian population.

METHODS

Whole exome sequencing (WES) was conducted on DNA from 101 patients in the Iranian Hereditary Colorectal Cancer Registry (IHCCR). The cohort included 63 high-risk Lynch Syndrome (LS) patients and 38 colorectal polyposis patients. Germline variants and phenotype spectrum were assessed. Relatives of individuals with the mutations received counseling and cascade testing. Gene ontology and protein-protein interaction (PPI) analyses were conducted to elucidate gene roles on protein function.

RESULTS

Pathogenic/likely pathogenic (P/LP) variants were identified in Lynch-related genes in 36.51% of patients. P/LP variants in non-Lynch genes (ATM, FH (mono-allelic), MSH3, PMS1, and TP53) were identified in 26.98% of patients. Among polyposis patients, 50% had P/LP variants in the APC gene, and 15.79% had P/LP variants in the MUTYH gene. Additionally, 7.89% carried P/LP variants in non-FAP/MAP genes (BLM, BRCA2, and PTEN). MLH1 variants were most common in exons 10 and 18, MSH2 in exon 12, and APC gene in exon 16. Cascade testing identified 50% of the tested relatives (40/80). Topology analysis of the protein-protein interaction networks in high-risk LS cases highlighted stronger connections among nodes for genes such as TP53, ATM, POLD1, CDH1, MUTYH, WRN, NOTCH1, SMAD4, ERCC4, ERCC1, and MSH3. These genes were associated with high penetrance in CRC. The protein-protein interaction analyses of polyposis patients indicated that genes like POLE, MSH6, MSH2, BRCA2, BRCA1, MLH1, TOPBP1, BLM, RAD50, MUTYH, MSH3, MLH3, PTEN, BRIP1, and POLK had a higher degree value and were also associated with high penetrance. Gene ontology and protein-protein interaction (PPI) analysis showed that some of the top-scoring non-Lynch genes were TP53, ATM, POLD1, CDH1, MUTYH, WRN, NOTCH1, SMAD4, ERCC4, ERCC1, and MSH3.

CONCLUSIONS

The study identified crucial germline variants for hereditary polyposis and non-polyposis CRC pathogenesis in the Iranian population. A selective strategy and cascade genetic testing are recommended for the diagnosis of hereditary colorectal cancer syndromes.

Whole genome joint analysis reveals ATM:C.1564_1565del variant segregating with Ataxia-Telangiectasia and breast cancer

ATM gene is implicated in the development of breast cancer in the heterozygous state, and Ataxia-telangiectasia (A-T) in a homozygous or compound heterozygous state. Ataxia-telangiectasia (A-T) is a rare cerebellar ataxia syndrome presenting with progressive neurologic impairment, telangiectasia, and an increased risk of leukemia and lymphoma. Although the role of ATM, separately, in association with A-T and breast cancer is well documented, there is a limited number of studies investigating ATM variants when segregating with both phenotypes in the same family. Here, using joint analysis and whole genome sequencing, we investigated ATM c.1564_1565del in a family with one homozygous member presenting with A-T (OMIM # 208900) and three heterozygous members, of whom one had breast cancer (OMIM #114480). To our knowledge, this is the first study of ATM c.1564_1565del segregation with both A-T and breast cancer phenotypes within the same kindred. This study highlights the need for a comprehensive genomic approach in the appropriate cancer risk management of heterozygote carriers of ATM in families with A-T.

Insights into Clinical Disorders in Cowden Syndrome: A Comprehensive Review

PTEN Hamartoma Tumour Syndrome (PHTS) encompasses diverse clinical phenotypes, including Cowden syndrome (CS), Bannayan-Riley-Ruvalcaba syndrome (BRRS), Proteus syndrome (PS), and Proteus-like syndrome. This autosomal dominant genetic predisposition with high penetrance arises from heterozygous germline variants in the PTEN tumour suppressor gene, leading to dysregulation of the PI3K/AKT/mTOR signalling pathway, which promotes the overgrowth of multiple and heterogenous tissue types. Clinical presentations of CS range from benign and malignant disorders, affecting nearly every system within the human body. CS is the most diagnosed syndrome among the PHTS group, notwithstanding its weak incidence (1:200,000), for which it is considered rare, and its precise incidence remains unknown among other important factors. The literature is notably inconsistent in reporting the frequencies and occurrences of these disorders, adding an element of bias and uncertainty when looking back at the available research. In this review, we aimed to highlight the significant disparities found in various studies concerning CS and to review the clinical manifestations encountered in CS patients. Furthermore, we intended to emphasize the great significance of early diagnosis as patients will benefit from a longer lifespan while being unceasingly advised and supported by a multidisciplinary team.

The complexity of phosphatase and tensin homolog hamartoma tumor syndrome: A case report

Germline pathogenic variants found in the phosphatase and tensin homolog gene are associated with a range of rare syndromes that collectively fall under the umbrella of phosphatase and tensin homolog hamartoma tumor syndromes. Due to the wide array of possible clinical presentations and the varying degrees of symptom severity, many individuals with phosphatase and tensin homolog hamartoma tumor syndromes might remain undiagnosed for an extended period. We describe a case of a male child who received the diagnosis at the age of 12. His clinical features included macrocephaly, hypertrophy in the left arm, thyroid nodules, penile freckles, developmental delay, and an autism spectrum disorder. Whole exome sequencing revealed a de novo heterozygous variant in the phosphatase and tensin homolog. The case highlights the diverse and complex nature of phosphatase and tensin homolog hamartoma tumor syndromes, emphasizing the necessity for early diagnosis, multidisciplinary care, and surveillance protocols, offering the potential for improved prognostic outcomes and enhanced quality of life for affected individuals.