Elizabeth MacNamara

The Founder Mutation MSH2*1906G→C Is an Important Cause of Hereditary Nonpolyposis Colorectal Cancer in the Ashkenazi Jewish Population

Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by mutations in the mismatch-repair genes. We report here the identification and characterization of a founder mutation in MSH2 in the Ashkenazi Jewish population. We identified a nucleotide substitution, MSH2*1906G-->C, which results in a substitution of proline for alanine at codon 636 in the MSH2 protein. This allele was identified in 15 unrelated Ashkenazi Jewish families with HNPCC, most of which meet the Amsterdam criteria. Genotype analysis of 18 polymorphic loci within and flanking MSH2 suggested a single origin for the mutation. All colorectal cancers tested showed microsatellite instability and absence of MSH2 protein, by immunohistochemical analysis. In an analysis of a population-based incident series of 686 Ashkenazi Jews from Israel who have colorectal cancer, we identified 3 (0.44%) mutation carriers. Persons with a family history of colorectal or endometrial cancer were more likely to carry the mutation than were those without such a family history (P=.042), and those with colorectal cancer who carried the mutation were, on average, younger than affected individuals who did not carry it (P=.033). The mutation was not detected in either 566 unaffected Ashkenazi Jews from Israel or 1,022 control individuals from New York. In hospital-based series, the 1906C allele was identified in 5/463 Ashkenazi Jews with colorectal cancer, in 2/197 with endometrial cancer, and in 0/83 with ovarian cancer. When families identified by family history and in case series are included, 25 apparently unrelated Ashkenazi Jewish families have been found to harbor this mutation. Although this pathogenic mutation is not frequent in the Ashkenazi Jewish population (accounting for 2%-3% of colorectal cancer in those whose age at diagnosis is <60 years), it is highly penetrant and accounts for approximately one-third of HNPCC in Ashkenazi Jewish families that fulfill the Amsterdam criteria.

Postoperative parathyroid hormone level as a predictor of post-thyroidectomy hypocalcemia.

OBJECTIVES To evaluate levels of parathyroid hormone following total thyroidectomy in order to ascertain its ability to predict postoperative hypocalcemia. To establish standardized criteria permitting the safe discharge of total thyroidectomy patients within 13 hours of surgery. METHODS This is a prospective study in which parathyroid hormone levels were tested in 54 consecutive patients who underwent total thyroidectomy. Levels were measured postoperatively at 6, 12, and 20 hours. Corrected calcium levels were also measured at 6, 12, and 20 hours in accordance with the preexisting protocol. RESULTS Statistical analysis demonstrates that patients with corrected calcium levels greater than or equal to 2.14 mmol/L and parathyroid hormone levels greater than or equal to 28 ng/L at 12 hours post-thyroidectomy can be discharged without further need for calcium monitoring. The analysis also demonstrates that patients with 12-hour parathyroid hormone levels less than or equal to 20 ng/L are at significant risk of developing hypocalcemia. CONCLUSION Parathyroid hormone levels in conjunction with corrected calcium values are accurate predictors of the calcium trends of post-thyroidectomy patients. Implementation of this protocol can result in shorter hospital stays for the majority of post-thyroidectomy patients, which can translate into substantial cost savings for the health care system.

Germline truncating mutations in both MSH2 and BRCA2 in a single kindred

There has been interest in the literature in the possible existence of a gene that predisposes to both breast cancer (BC) and colorectal cancer (CRC). We describe the detailed characterisation of one kindred, MON1080, with 10 cases of BC or CRC invasive cancer among 26 first-, second- or third-degree relatives. Linkage analysis suggested that a mutation was present in BRCA2. DNA sequencing from III: 22 (diagnosed with lobular BC) identified a BRCA2 exon 3 542G>T (L105X) mutation. Her sister (III: 25) had BC and endometrial cancer and carries the same mutation. Following immunohistochemical and microsatellite instability studies, mutation analysis by protein truncation test, cDNA sequencing and quantitative real-time PCR revealed a deletion of MSH2 exon 8 in III: 25, confirming her as a double heterozygote for truncating mutations in both BRCA2 and MSH2. The exon 8 deletion was identified as a 14.9 kb deletion occurring between two Alu sequences. The breakpoint lies within a sequence of 45 bp that is identical in both Alu sequences. In this large BC/CRC kindred, MON1080, disease-causing truncating mutations are present in both MSH2 and BRCA2. There appeared to be no increased susceptibility to the development of colorectal tumours in BRCA2 mutation carriers or to the development of breast tumours in MSH2 mutation carriers. Additionally, two double heterozygotes did not appear to have a different phenotype than would be expected from the presence of a mutation in each gene alone.

Postoperative parathyroid hormone levels in conjunction with corrected calcium values as a predictor of post-thyroidectomy hypocalcemia : Review of outcomes 1 year after the implementation of a new protocol

OBJECTIVES To determine the effectiveness of post-thyroidectomy parathyroid hormone (PTH) levels in conjunction with corrected calcium values as predictors of patients at risk of developing hypocalcemia. METHODS This is a follow-up study reviewing the results of a newly implemented post-thyroidectomy algorithm. The changes in management from the previous protocol involve decision making based on the 12-hour corrected calcium and PTH levels, as well as the 1-hour PTH value. The study involved 120 patients separated into two groups: 60 prior to implementation of the protocol and 60 following the implementation of the protocol. Patients having completion thyroidectomy, neck dissections, or parathyroidectomy were excluded. RESULTS Since the implementation of the new protocol, there has been a reduction in the rate of transient hypocalcemia (25% to 12%; p = .059), fewer blood tests (23 to 15 per patient), and earlier patient discharges. CONCLUSIONS The new algorithm is effective in detecting patients who are not at risk of developing hypocalcemia at 12 hours. This has led to significant cost savings at our institution. Moreover, calcium supplementation based on the 1-hour PTH level has coincided with a reduction in cases of transient hypocalcemia.

Effects of vitamin C and vitamin D administration on mood and distress in acutely hospitalized patients

BACKGROUND Hypovitaminosis C and D are highly prevalent in acute-care hospitals. Malnutrition with regard to these vitamins has been linked to mood disturbance and cognitive dysfunction. OBJECTIVE The objective was to determine whether vitamin C or D supplementation improves mood state or reduces psychological distress in acutely hospitalized patients with a high prevalence of hypovitaminosis C and D. DESIGN A randomized, double-blind, active-control clinical trial compared the effects of vitamin C (500 mg twice daily) with those of high-dose vitamin D (5000 IU/d) on mood (Profile of Mood States) and psychological distress (Distress Thermometer). RESULTS Vitamin C provided for a mean of 8.2 d increased plasma vitamin C concentrations to normal (P < 0.0001) and was associated with a 71% reduction in mood disturbance (P = 0.0002) and a 51% reduction in psychological distress (P = 0.0002). High-dose vitamin D provided for a mean of 8.1 d increased plasma 25-hydroxyvitamin D [25(OH)D] concentrations (P < 0.0001), but not into the normal range, and had insignificant effects on mood (P = 0.067) and distress (P = 0.45). The changes in mood and distress in the vitamin C group were greater than those in the vitamin D group (P = 0.045 for mood; P = 0.009 for distress). CONCLUSIONS Short-term therapy with vitamin C improves mood and reduces psychological distress in acutely hospitalized patients with a high prevalence of hypovitaminosis C and D. No conclusion is possible regarding the effects of vitamin D because the dose and duration of therapy were insufficient to raise 25(OH)D concentrations into the normal range. This trial was registered at clinicaltrials.gov as NCT01630720.

Cost savings associated with post-thyroidectomy parathyroid hormone levels

OBJECTIVES: A 1-hour post-thyroidectomy parathyroid hormone (PTH) level of ≤8 ng/L is predictive of patients who will develop hypocalcemia and guides early supplementation with calcium and vitamin D. However, most hypocalcemic patients fail to meet this criterion. The goal of this study was to determine whether PTH ≤ 15 ng/L could be used as a better predictor of hypocalcemia. STUDY DESIGN, SUBJECTS, AND METHODS: This retrospective study involved 270 thyroidectomy patients (2004-2006). PTH and calcium levels, length of admission, supplementation, and rates of hypocalcemia were recorded. RESULTS: Forty-three percent (26/60) of patients developing hypocalcemia met the PTH ≤ 8 ng/L cut-off. In contrast, 80% (48/60) of patients developing hypocalcemia had a PTH ≤ 15 ng/L. Two point two percent of patients had a 1-hour PTH ≤ 15 ng/L and failed to develop hypocalcemia, for a specificity of 97%. CONCLUSIONS: A 1-hour PTH cut-off of ≤15 ng/L for prophylactic supplementation should allow the prevention of the majority of cases of hypocalcemia, leading to significant cost savings by shortening hospital stays.

Role of molecular diagnostic testing in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer families

PURPOSE: Genetic tests are available for familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer. The goal of this review was to develop an algorithm for application of molecular diagnostic techniques to the management of hereditary colorectal carcinoma and to familiarize the clinician with the vocabulary of molecular genetic testing for hereditary colorectal carcinoma. METHODS: Studies examining the clinical use of genetic testing for hereditary colorectal carcinoma syndromes are evaluated. Recent advances in molecular genetic technology are reviewed, and clinical management as practiced here and elsewhere is outlined. RESULTS: This review is a guide to the most reliable molecular diagnostic techniques. Three key questions are answered: who, when, and how to test. CONCLUSIONS: When integrated with existing testing protocols for colorectal carcinoma and when applied with appropriate caveats, particularly regarding interpretation of negative results, genetic testing can result in improved management of patients and families.

An MLH1 haplotype is over-represented on chromosomes carrying an HNPCC predisposing mutation in MLH1

Background: The mismatch repair gene, MLH1, appears to occur as two main haplotypes at least in white populations. These are referred to as A and G types with reference to the A/G polymorphism at IVS14-19. On the basis of preliminary experimental data, we hypothesised that deviations from the expected frequency of these two haplotypes could exist in carriers of disease associated MLH1 germline mutations. Methods: We assembled a series (n=119) of germline MLH1 mutation carriers in whom phase between the haplotype and the mutation had been conclusively established. Controls, without cancer, were obtained from each contributing centre. Cases and controls were genotyped for the polymorphism in IVS14. Results: Overall, 66 of 119 MLH1 mutations occurred on a G haplotype (55.5%), compared with 315 G haplotypes on 804 control chromosomes (39.2%, p=0.001). The odds ratio (OR) of a mutation occurring on a G rather than an A haplotype was 1.93 (95% CI 1.29 to 2.91). When we compared the haplotype frequencies in mutation bearing chromosomes carried by people of different nationalities with those seen in pooled controls, all groups showed a ratio of A/G haplotypes that was skewed towards G, except the Dutch group. On further analysis of the type of each mutation, it was notable that, compared with control frequencies, deletion and substitution mutations were preferentially represented on the G haplotype (p=0.003 and 0.005, respectively). Conclusion: We have found that disease associated mutations in MLH1 appear to occur more often on one of only two known ancient haplotypes. The underlying reason for this observation is obscure, but it is tempting to suggest a possible role of either distant regulatory sequences or of chromatin structure influencing access to DNA sequence. Alternatively, differential behaviour of otherwise similar haplotypes should be considered as prime areas for further study.

Preoperative parathyroid hormone levels as a predictor of postthyroidectomy hypocalcemia.

Objectives. The goal of the present study is to determine whether a decline in the 1-hour postoperative parathyroid hormone (PTH) level relative to the preoperative level is predictive of hypocalcemia. Methods. This is a retrospective study involving 142 consecutive patients who underwent total thyroidectomy. Changes in preoperative PTH levels were then compared with the 1-hour levels. Results. Thirty-four of 142 patients (23.9%) who underwent total thyroidectomy developed hypocalcemia. Thirty-one of the 34 patients who became hypocalcemic had a 1-hour postoperative PTH drop of 70% or more when compared with the preoperative value (sensitivity = 91%, specificity = 98%, positive predictive value = 94%, and negative predictive value = 97%). Conclusion. A decline in the preoperative PTH level of 70% or greater at 1 hour following total thyroidectomy appears to be a reliable predictor of patients at risk of developing hypocalcemia. By allowing thyroid surgeons to identify these patients in the early postoperative period, calcium supplementation can be initiated sooner.

The value of multi-modal gene screening in HNPCC in Quebec: three mutations in mismatch repair genes that would have not been correctly identified by genomic DNA sequencing alone.

Hereditary non-polyposis colorectal cancer (HNPCC) is a dominantly inherited cancer syndrome caused by a mutation in one of the mismatch repair genes, most frequently MLH1 or MSH2. The rate of mutation detection is influenced by many factors, including the diagnostic methods used. Large deletions, which occur frequently in MLH1 and MSH2, are not detected by exon-by-exon screening methods. Here, we describe three mutations in mismatch repair genes detected using a screening protocol that combines protein truncation test (PTT) analysis and multiplex ligation-dependent probe amplification (MLPA) with genomic and cDNA sequencing. Two of these mutations consist of large deletions in MLH1 that were detected by both MLPA and PTT but that would have been missed by genomic DNA sequencing. The third is a large deletion in MSH2 that could not be detected by PTT because of its location relative to the primers used to amplify the cDNA, or by sequencing. This mutation was detected by MLPA.