Cancer risk in MLH1, MSH2 and MSH6 mutation carriers; different risk profiles may influence clinical management

Background

Lynch syndrome (LS) is associated with a high risk for colorectal cancer (CRC) and extracolonic malignancies, such as endometrial carcinoma (EC). The risk is dependent of the affected mismatch repair gene. The aim of the present study was to calculate the cumulative risk of LS related cancers in proven MLH1, MSH2 and MSH6 mutation carriers.

Methods

The studypopulation consisted out of 67 proven LS families. Clinical information including mutation status and tumour diagnosis was collected. Cumulative risks were calculated and compared using Kaplan Meier survival analysis.

Results

MSH6 mutation carriers, both males and females had the lowest risk for developing CRC at age 70 years, 54% and 30% respectively and the age of onset was delayed by 3-5 years in males. With respect to endometrial carcinoma, female MSH6 mutation carriers had the highest risk at age 70 years (61%) compared to MLH1 (25%) and MSH2 (49%). Also, the age of EC onset was delayed by 5-10 years in comparison with MLH1 and MSH2.

Conclusions

Although the cumulative lifetime risk of LS related cancer is similar, MLH1, MSH2 and MSH6 mutations seem to cause distinguishable cancer risk profiles. Female MSH6 mutation carriers have a lower CRC risk and a higher risk for developing endometrial carcinoma. As a consequence, surveillance colonoscopy starting at age 30 years instead of 20-25 years is more suitable. Also, prophylactic hysterectomy may be more indicated in female MSH6 mutation carriers compared to MLH1 and MSH2 mutation carriers.     

Mitochondrial dysfunction in skeletal muscle of children with cardiomyopathy

OBJECTIVES: This study sought to examine skeletal muscle of children with cardiomyopathy (CM) for changes in mitochondrial enzyme activities and in mitochondrial DNA (mtDNA). BACKGROUND: Heart mitochondrial enzymatic activity defects have been often found in dilated and hypertrophic CM. The defects primarily involve the activities of the electron transport system and oxidative phosphorylation pathway including respiratory complexes I, III, IV, and V. METHODS: Skeletal muscle biopsies of 8 children with CM were examined for specific mitochondrial enzyme activities, mtDNA copy number and the presence of pathogenic mutations and deletions in mtDNA. RESULTS: A marked deficiency in specific mitochondrial enzyme activities was found in 6 of 8 patients in skeletal muscle as well as in 2 of 3 hearts of those in whom cardiac tissue was available. Specific activity defects were found in complex I (2 cases), complex III (5 cases), complex IV (3 cases), and complex V (4 cases). Complex II and citrate synthase activities were unaffected. None of the previously reported pathogenic mutations associated with CM were detected, nor was there any evidence of mtDNA depletion. The incidence of defective respiratory complex activities in skeletal muscle was similar to the incidence of defective complex activities previously reported in cardiac tissue. CONCLUSIONS: Mitochondrial analysis of skeletal muscle is warranted in the overall clinical evaluation of children with CM, and particularly before consideration for cardiac transplantation.     

Radiofrequency catheter ablation in a haemodynamically compromised premature neonate with hydrops fetalis

A preterm infant was born at 35 weeks gestation after failed antenatal antiarrhythmic therapy. The infant had an incessant supraventricular tachycardia, impaired ventricular function and hypotension and failed to respond to adenosine, cardioversion and intravenous amiodarone. After resuscitation from cardiovascular collapse, a successful radiofrequency catheter ablation (RFA) of a left free wall atrioventricular pathway was performed at 24 h of age without extracorporeal support. The infant is normal on follow up at 12 months of age. Whilst most fetal and neonatal supraventricular tachyarrhythmias respond to antiarrhythmic medications and RFA is not required, this is the earliest RFA to be performed on a premature infant when antiarrhythmics have failed.     

Six-month follow-up of children with obstructive sleep apnoea

OBJECTIVES: This study examined prospectively changes in development, temperament and sleep related behaviour in children referred for obstructive sleep apnoea (OSA) and polysomnographic sleep study, some of whom had surgical intervention. METHODOLOGY: Using a prospective cohort study design, parents of 56 children referred for OSA completed sleep and temperament questionnaires and their child was assessed developmentally at the time of the polysomnographic sleep study. Forty (72%) of the children were neurologically normal. At 6 months, 42 children were reassessed using sleep and temperament questionnaires and a developmental assessment. After excluding the primary snorers, subjects were categorised as having had intervention (n = 24) or not (n = 15), and differences over the 6-month period in Griffiths scores, temperament and sleep related behaviour were examined. RESULTS: Regardless of intervention status, there was an improvement in night-time and day-time sleep behaviour for the total group, though the extent of improvement was more marked in the intervention group. For the neurologically normal children, improvement in the sleep behaviour was only significant for the intervention group (P < 0.05). Intervention did not result in any significant changes in Griffiths developmental score or temperament. CONCLUSION: Surgical intervention improves sleep behaviour in children though not temperament or development.     

Effect of vitamin E on chromosomal aberrations in lymphocytes from patients with Down's syndrome

A possible protective effect of vitamin E (DL-alpha-tocopherol) on chromosomal damage was evaluated in lymphocytes from patients with Down's syndrome (DS) and from controls. This included the analysis of the basal and G2 chromosomal aberration frequencies in lymphocytes cultured with and without 100 microM vitamin E. The chromosomal damage in G2 was determined by scoring the number of chromosomal aberrations in lymphocyte cultures treated with 5 mM caffeine, 2 h before harvesting. Vitamin E treatment decreased the basal and G2 chromosomal aberrations both in control and DS lymphocytes. In DS cells, this protective effect, expressed as a decrease in the chromosomal damage, was greater (50%) than in controls (30%). These results suggest that the increment in basal and G2 aberrations yield in DS lymphocytes may be related to the increase in oxidative damage reported in these patients.