A large deletion of chromosome 5q22.1-22.2 associated with sparse type of familial adenomatous polyposis: report of a case

Genomic insights into familial adenomatous polyposis: unraveling a rare case with whole APC gene deletion and intellectual disability

A young patient diagnosed with advanced colon cancer and liver metastasis was found to have familial adenomatous polyposis (FAP) through comprehensive genomic analysis. Whole-genome array comparative genomic hybridization (aCGH) revealed germline deletions at chromosome 5q22.1-22.2 encompassing the entire APC gene. The patient and her son exhibited mild intellectual disability without developmental delay. This case highlights the need for further exploration of the characteristics associated with whole APC deletions. aCGH is a valuable tool for studying FAP and provides a detailed analysis of large deletions.

Interstitial Deletion of 5q22.2q23.1 Including APC and TSSK1B in a Patient with Adenomatous Polyposis and Asthenoteratozoospermia

Interstitial 5q22 deletions are relatively rare and usually represented by severe clinical features such as developmental delay and growth retardation. Here, we report a 23-year-old male patient, referred to our laboratory for genetic confirmation of possible familial adenomatous polyposis. MLPA and the subsequent array CGH identified an approximately 8-Mb-sized deletion in the 5q22.2q23.1 locus. Further analysis of the deleted region and the genes within suggested a possible role for the TSSK1B (testis-specific serine/threonine kinase 1) gene in the patient's reproductive capacity. Semen analysis confirmed that the patient's reproductive capability was impaired, and that he suffered from asthenoteratozoospermia. Analysis of the azoospermia factor region on the Y chromosome revealed no microdeletions. Further sequencing tests could not find an alternative explanation for the patient's infertility. This case demonstrates a possible role of TSSK1B in male reproduction.

Gardner syndrome with maxillofacial manifestation: A case report

Gardner syndrome is a hereditary disease in which patients develop gastrointestinal polyps, osteomas, desmoid tumors, epidermoid cysts, fibromas, lipomas, and retinal lesions. Dental abnormalities such as supernumerary or impacted teeth, odontomas and dentigerous cysts are also reported. The most serious concern in this syndrome is the extremely high risk of gastrointestinal polyps undergoing malignant transformation. Since the maxillofacial findings usually precede gastrointestinal polyps, the dentist plays a crucial role in the diagnosis of Gardner syndrome, and panoramic radiography is an important tool in the diagnosis of the disease. We report here a case of Gardner syndrome in a patient showing mandibular osteomas and impacted teeth. Also, cases of Gardner syndrome with maxillofacial manifestations reported in the literature were reviewed and compared with ours. According to the findings, osteomas are important manifestations of this syndrome, and regardless of the absence of family history of intestinal polyposis, their occurrence should prompt diagnostic evaluation for this disease.

A novel large germ line deletion in adenomatous polyposis coli (APC) gene associated with familial adenomatous polyposis

Background

Familial adenomatous polyposis (FAP) is a familial colorectal cancer predisposition syndrome characterized by the development of numerous colorectal polyps, which is inherited in an autosomal dominant manner. FAP is caused by germ line mutations in adenomatous polyposis coli (APC) gene. Here, we described the identification of a causative APC gene deletion associated with FAP in an Iranian family.

Methods

Diagnosis of FAP was based on clinical findings, family history, and medical records (colonoscopy and histopathological data) after the patients were referred to Reza Radiotherapy and Oncology Center, Iran, for colonoscopy. Blood samples were collected, and genomic DNA was extracted. APC mutation screening was conducted by target next‐generation sequencing and quantitative real‐time PCR.

Results

A novel heterozygous large deletion mutation, c.(135+1_136–1)_(*2113+1_*2114–1) spanning exon 3 to 16 [EX3_16 DEL] of APC gene (GenBank Accession# MG712911), was detected in a proband and all her affected relatives in five generations, which was absent in unaffected family members and normal controls.

Conclusions

This novel deletion is the first report, describing the largest deletion of APC gene. Our novel finding contributes to a more comprehensive database of germ line mutations of APC gene that could be used in medical practice for the molecular diagnosis, risk assessment susceptibility of the disease for the FAP patients.

Disruption of the APC gene by t(5;7) translocation in a Turcot family

Turcot syndrome (TS) refers to the combination of colorectal polyps and primary tumours of the central nervous system. TS is a heterogeneous genetic condition due to APC and/or mismatch repair germline mutations. When APC is involved the vast majority of mutations are truncating, but in approximately 20%-30% of patients with familial polyposis no germline mutation can be found. A 30-year-old Caucasian woman with a positive pedigree for TS was referred to our Genetic Counselling Service. She was negative for APC and MUTYH but showed a reciprocal balanced translocation t(5;7)(q22;p15) at chromosome analysis. FISH analysis using specific BAC probes demonstrated that 5q22 breakpoint disrupted the APC gene. Transcript analysis by MLPA and digital PCR revealed that the cytogenetic rearrangement involving the 3' end of the APC gene caused a defective expression of a truncated transcript. This result allowed cytogenetic analysis to be offered to all the other family members and segregation analysis clearly demonstrated that all the carriers were affected, whereas non-carriers did not have the polyposis. A cytogenetic approach permitted the identification of the mutation-causing disease in this family, and the segregation analysis together with the transcript study supported the pathogenetic role of this mutation. Karyotype analysis was used as a predictive test in all members of this family. This family suggests that clinically positive TS and FAP cases, which test negative with standard molecular analysis, could be easily and cost-effectively resolved by a classical and molecular cytogenetic approach.