Childhood cancers in families with and without Lynch syndrome

Inheritance of a germline mutation in one of the DNA mismatch repair (MMR) genes or the EPCAM gene is associated with an increased risk of colorectal cancer, endometrial cancer, and other adult malignancies (Lynch syndrome). The risk of childhood cancers in Lynch syndrome families, however, is not well studied. Using data from the Colon Cancer Family Registry, we compared the proportion of childhood cancers (diagnosed before 18 years of age) in the first-, second-, and third-degree relatives of 781 probands with a pathogenic mutation in one of the MMR genes; MLH1 (n = 275), MSH2 (n = 342), MSH6 (n = 99), or PMS2 (n = 55) or in EPCAM (n = 10) (Lynch syndrome families), with that of 5073 probands with MMR-deficient colorectal cancer (non-Lynch syndrome families). There was no evidence of a difference in the proportion of relatives with a childhood cancer between Lynch syndrome families (41/17,230; 0.24%) and non-Lynch syndrome families (179/94,302; 0.19%; p = 0.19). Incidence rate of all childhood cancers was estimated to be 147 (95% CI 107-206) per million population per year in Lynch syndrome families and 115 (95% CI 99.1-134) per million population per year in non-Lynch syndrome families. There was no evidence for a significant increase in the risk of all childhood cancers, hematologic cancers, brain and central nervous system cancers, Lynch syndrome-associated cancers, or other cancers in Lynch syndrome families compared with non-Lynch syndrome families. Larger studies, however, are required to more accurately define the risk of specific individual childhood cancers in Lynch syndrome families.

Phenotypic and genotypic characterisation of biallelic mismatch repair deficiency (BMMR-D) syndrome

Lynch syndrome, the most common inherited colorectal cancer syndrome in adults, is an autosomal dominant condition caused by heterozygous germ-line mutations in DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. Inheriting biallelic (homozygous) mutations in any of the MMR genes results in a different clinical syndrome termed biallelic mismatch repair deficiency (BMMR-D) that is characterised by gastrointestinal tumours, skin lesions, brain tumours and haematologic malignancies. This recently described and under-recognised syndrome can present with adenomatous polyps leading to early-onset small bowel and colorectal adenocarcinoma. An important clue in the family history that suggests underling BMMR-D is consanguinity. Interestingly, pedigrees of BMMR-D patients typically show a paucity of Lynch syndrome cancers and most parents are unaffected. Therefore, a family history of cancers is often non-contributory. Detection of BMMR-D can lead to more appropriate genetic counselling and the implementation of targeted surveillance protocols to achieve earlier tumour detection that will allow surgical resection. This review describes an approach for diagnosis and management of these patients and their families.

Lynch syndrome: a pediatric perspective

Colorectal cancer is a rare disease in the pediatric age group and, when present, suggests an underlying genetic predisposition. The most common hereditary colon cancer susceptibility condition, Lynch syndrome (LS), previously known as hereditary nonpolyposis colorectal cancer, is an autosomal dominant condition caused by a germline mutation in 1 of 4 DNA mismatch repair (MMR) genes: MLH1, MSH2, MSH6, or PMS2. The mutation-prone phenotype of this disorder is associated with gastrointestinal, endometrial, and other cancers and is now being identified in both symptomatic adolescents with malignancy as well in asymptomatic mutation carriers who are at risk for a spectrum of gastrointestinal and other cancers later in life. We review the DNA MMR system, our present understanding of LS in the pediatric population, and discuss the newly identified biallelic form of the disease known as constitutional mismatch repair deficiency syndrome. Both family history and tumor characteristics can help to identify patients who should undergo genetic testing for these cancer predisposition syndromes. Patients who carry either single allele (LS) or double allele (constitutional mismatch repair deficiency syndrome) mutations in the MMR genes benefit from cancer surveillance programs that target both the digestive and extraintestinal cancer risk of these diseases. Because spontaneous mutation in any one of the MMR genes is extremely rare, genetic counseling and testing are suggested for all at-risk family members.

Oncologic surveillance for subjects with biallelic mismatch repair gene mutations: 10 year follow-up of a kindred

BACKGROUND

Heterozygous germline mutations in DNA mismatch repair (MMR) genes cause Lynch syndrome. Biallelic MMR mutations cause a distinct syndrome characterized by brain tumors, lymphoid malignancies, and gastrointestinal cancers during childhood. These children usually succumb to multiple cancers before adulthood. We developed a surveillance protocol aiming at early detection for these individuals and report the 10-year experience with a kindred.

METHODS

On the basis of genetic testing and early age tumors, the kindred started a cancer surveillance protocol based on the crude estimates of cancer risks and available cancer screening: imaging, endoscopy, and hematologic tests.

RESULTS

Over the 10-year follow-up period, the screening protocol detected 15 tumors. These included three high-grade adenomatous colonic polyps and two colon cancers. In one child, MRI revealed an asymptomatic anaplastic astrocytoma which was treated by complete resection and radiation. All three cancers identified during surveillance were small and asymptomatic at diagnosis. The two sisters are currently 16 and 18 years of age with no evidence of malignant disease. Both parents have annual colonoscopies and the father at 43 years had two colonic adenomatous polyps.

CONCLUSIONS

We report on the long-term outcome in patients with biallelic MMR mutations who benefited from prophylactic cancer surveillance. Genetic screening and subsequent surveillance led to earlier recognition of asymptomatic tumors at stages more amenable to resection and probable cure. Multicenter collaboration and implementation of surveillance guidelines is necessary to further determine genotype-phenotype correlations.

The gastrointestinal phenotype of germline biallelic mismatch repair gene mutations

OBJECTIVES

A novel cancer syndrome associated with biallelic mismatch repair (MMR) mutations has been described recently. Patients presenting with childhood-onset gastrointestinal (GI) cancers may carry biallelic MMR mutations and have a distinct phenotype from classic Lynch syndrome. The aim of this study was to characterize patients with GI small bowel and/or colorectal cancers (CRCs) who have germline biallelic MMR mutations.

METHODS

A search of a Canadian GI cancer registry and literature review to identify patients with biallelic MMR was conducted.

RESULTS

The database identified 237 patients with intestinal cancer diagnosed before the age of 35 years. Five (2.1%) patients had biallelic MMR mutations. Overall, 32 individuals, from 29 families, with biallelic MMR gene mutations and GI cancers were identified by the registry and literature review. Among the 29 patients with CRCs, the mean age of first cancer diagnosis was 16.4 years (range: 5-28). More than one-third of patients had multiple colorectal adenomas (>10 polyps). Six individuals with biallelic MMR gene mutations have been reported with small bowel adenocarcinoma (mean age 20 years (range: 11-41)). Café-au-lait (CAL) macules were reported in 72% and, based on mutation analysis, consanguinity was suspected in 52% of kindred. Of the 29 kindred, 19 (66%) had PMS2 mutations, 6 (21%) had MSH6 mutations, 3 (10%) had MLH1 mutations, and 1 (3%) had MSH2 mutation.

CONCLUSIONS

Biallelic MMR mutations are an underrecognized cause of small bowel and colonic cancers in children and young adults. This distinct phenotype includes multiple adenomatous polyps and CAL skin lesions. It is important to identify such patients, so that families can be referred for genetic testing and counseling.

Colonic polyps in children and adolescents

Colonic polyps most commonly present with rectal bleeding in children. The isolated juvenile polyp is the most frequent kind of polyp identified in children. 'Juvenile' refers to the histological type of polyp and not the age of onset of the polyp. Adolescents and adults with multiple juvenile polyps are at a significant risk of intestinal cancer. The challenge for adult and pediatric gastroenterologists is determining the precise risk of colorectal cancer in patients with juvenile polyposis syndrome. Attenuated familial adenamatous polyposis (AFAP) can occur either by a mutation at the extreme ends of the adenomatous polyposis coli gene or by biallelic mutations in the mutY homologue (MYH) gene. The identification of MYH-associated polyposis as an autosomal recessive condition has important implications for screening and management strategies. Adult and pediatric gastroenterologists need to be aware of the underlying inheritance patterns of polyposis syndromes so that patients and their families can be adequately evaluated and managed. Colonic polyps, including isolated juvenile polyps, juvenile polyposis syndrome, FAP, AFAP and MYH-associated polyposis, are discussed in the present review.

Genetic predisposition to colorectal cancer: new pieces in the pediatric puzzle

Colorectal cancer is rare in childhood. The 2 best characterized familial syndromes, hereditary nonpolyposis colorectal cancer (HNPCC, Lynch syndrome) and familial adenomatous polyposis (FAP), are autosomal dominant inherited disorders. HNPCC is relevant to pediatric gastroenterology practice because children and adolescents with underlying colorectal cancer can have germ-line mutations of mismatch repair genes. Recent attention has focused on characterizing genetic predisposition to attenuated FAP in individuals who do not have germ-line mutations in the APC gene. The identification of a second mechanistic explanation called MYH-associated polyposis (MAP), which is an autosomal-recessive condition, has important implications for both screening and management strategies. Hereditary colorectal cancer including HNPCC, FAP, attenuated FAP and MYH-associated polyposis in children are the subject of this review.

Magnetic resonance imaging to distinguish the type and severity of pediatric inflammatory bowel diseases

BACKGROUND

The distinction between ulcerative colitis and Crohn's disease is important, because treatment options and clinical course may vary. Magnetic resonance imaging (MRI) allows noninvasive transmural assessment of the intestine and may facilitate differentiation of ulcerative colitis from Crohn's disease. The objective of this prospective study was to determine whether MRI differentiates Crohn's disease from ulcerative colitis in children as effectively as colonoscopy with mucosal biopsies.

METHODS

Fifteen patients underwent colonoscopy with biopsies followed by abdominal MRI. The MRI diagnosis, determined by two radiologists independently completing a standardized form was compared with the gastroenterologic diagnosis.

RESULTS

After colonoscopy and review of histology, Crohn's disease was diagnosed in nine patients, ulcerative colitis in five, and indeterminate colitis in one, who was excluded from study. Agreement of the MRI diagnosis with the gastroenterologic diagnosis was 4 of 4 (100%) for ulcerative colitis, 4 of 10 (40%) for Crohn's disease considering both radiologists, and 5 of 10 (50%) for Crohn's disease for each radiologist individually. Percentage of enhancement by MRI did not correlate with the severity of inflammation determined at endoscopy among the patients with Crohn's disease (r = -0.3, P = 0.366). There was agreement on severity of inflammation in three of four patients with ulcerative colitis.

CONCLUSIONS

Current MRI interpretation of inflammatory bowel disease did not adequately recognize Crohn's disease in children. Therefore, colonoscopy with biopsy remains the most accurate tool for determining the type and severity of inflammatory bowel disease in children and adolescents.

Keeping an eye on Crohn's disease: orbital myositis as the presenting symptom

Episodic periorbital swelling due to presumed orbital inflammation and myositis caused intermittent apparent proptosis and was the presenting symptom of ileocecal Crohn's disease (CD) in a teenage female with a family history of autoimmune disorders and CD. Orbital myositis, a very rare extraintestinal manifestation of inflammatory bowel disease (IBD), likely represents a process of impaired immunoregulation related to the underlying intestinal inflammation. This rare manifestation of IBD simulates the more commonly encountered thyroid orbitopathy (ophthalmopathy), but IBD should be considered if all thyroid tests are negative. It is important to recognize that orbital myositis may be an extraintestinal manifestation of Crohn's disease so that the diagnosis can be made and appropriate therapy commenced.