Role of video capsule endoscopy in patients with constitutional mismatch repair deficiency (CMMRD) syndrome: report from the International CMMRD Consortium

Constitutional mismatch repair deficiency syndrome with atypical features caused by a homozygous MLH1 missense variant (c.1918C>A, p.(Pro640Thr)): a case report

Constitutional mismatch repair deficiency (CMMRD) syndrome is a rare autosomal recessive genetic disorder caused by biallelic germline mutations in one of the mismatch repair genes. Carriers are at exceptionally high risk for developing, typically in early life, hematological and brain malignancies, as well as cancers observed in Lynch syndrome. We report a homozygous MLH1 missense variant (c.1918C>A p.(Pro640Thr)) in a Tunisian patient with CMMRD syndrome and a family history of early-age colorectal cancer. The proband presented initially with colonic oligopolyposis and adenosquamous carcinoma of the caecum. He later developed several malignancies, including undifferentiated carcinoma of the parotid, grade 4 IDH-mutant astrocytoma, and ampulla of Vater adenocarcinoma. The patient was older than typical for this disease and had a remarkably prolonged survival despite developing four distinct aggressive malignancies. The current report highlights the challenges in assessing the pathogenicity of the identified variant and the remarkable phenotypic diversity in CMMRD.

High yield of surveillance in patients diagnosed with constitutional mismatch repair deficiency

Background

Constitutional mismatch repair deficiency (CMMRD) is a rare autosomal recessively inherited syndrome that is caused by biallelic pathogenic variants of the mismatch repair genes. It is characterised by the development of multiple tumours in the first and second decade of life including brain, gastrointestinal and haematological tumours often resulting in early death. In order to improve the prognosis of these patients, the European collaborative group ‘care for CMMRD’ developed a surveillance programme in 2014 and established a registry of patients with CMMRD in Paris. The aim of the study was to evaluate the outcome of this programme.

Methods

Twenty-two patients with a definitive diagnosis of CMMRD and with at least one follow-up study were selected from the registry. Medical data on the outcome of surveillance were collected from these patients.

Results

During a mean follow-up of 4 years, the programme detected eight malignant tumours including three brain tumours, three upper gastrointestinal cancers and two colorectal cancers. Most tumours could successfully be treated. In addition, many adenomas were detected in the duodenum, and colorectum and subsequently removed. Seven patients developed a symptomatic malignancy, including two brain tumours, one small bowel cancer and four haematological malignancies. At the end of the follow-up, 16 out of 22 patients (73%) who participated in the surveillance programme were still alive.

Conclusion

The study suggests a beneficial effect of surveillance of the digestive tract and brains.

Updates on progress in cancer screening for children with hereditary cancer predisposition syndromes

PURPOSE OF REVIEW

A significant proportion of pediatric cancer occurs in children with hereditary cancer predisposition syndromes. Their survival may be significantly improved and/or late effects diminished through screening for their greatly elevated cancer risks. Here, an overview of new developments in the field of pediatric cancer surveillance is provided.

RECENT FINDINGS

Consensus-based screening guidelines have been developed for most syndromes associated with childhood cancer risks. Studies evaluating the clinical utility of these screening regimens have also been emerging. This review focuses on three conditions for which consensus screening recommendations have been evolving in response to new evidence: Beckwith-Wiedemann syndrome, Li-Fraumeni syndrome, and constitutional mismatch repair deficiency syndrome. For each condition, recently proposed screening guidelines and relevant evidence are described and potential future directions for improving cancer surveillance practices are anticipated. Also, the implications of several recent studies exploring the psychosocial aspects of screening in these conditions are discussed.

SUMMARY

Significant strides have been made in cancer surveillance for children with hereditary cancer predisposition syndromes. A continued emphasis on consensus-driven screening guidelines and collaborative research evaluating the clinical utility of recommended screening methodologies will lead to further improvements in the clinical outcomes of these vulnerable children.