David E. C. Cole

Occult carcinoma in prophylactic oophorectomy specimens: Prevalence and association with BRCA germline mutation status

Prophylactic oophorectomy (PO) is an option for women at increased risk for ovarian carcinoma. In this study the value of intensive pathologic examination of PO specimens and accompanying resected tissues in the identification of occult carcinoma and any association of occult carcinoma with BRCA germline mutation status were ascertained. Specimens from 60 consecutive PO patients, who were not suspected of having any ovarian tumor at the time of surgery, were subjected to standardized, complete pathologic examination in a prospective study over an 8-year period. Extra-ovarian tissues were examined as well, but they were not subject to the same standardized protocol. Any occult carcinoma of the ovaries or fallopian tubes was noted. The BRCA status and follow-up of patients were obtained, if available. Fifty-five of the 60 PO specimens did not show any evidence of malignancy. Of the 32 patients in this group followed for >1 year, all are alive and well. The remaining five patients, all BRCA1 mutation positive, showed occult carcinoma of the ovaries and/or in situ or invasive carcinoma of a fallopian tube. One of these five patients has died of abdominal carcinomatosis; four continue to be well, but follow-up is <4 years in all cases. Occult carcinoma is present in a small proportion of BRCA-positive or unknown PO patients and may be of prognostic significance. The entire ovaries and tubes from PO patients should be submitted for histologic examination to identify malignancy.

Association of neural tube defects and folic acid food fortification in Canada

Many women do not receive folic acid supplements before conception. In response, most of Canadas cereal grain products were being fortified with folic acid by January, 1998, thereby providing an additional 0.1-0.2 mg per day of dietary folate to the Canadian population. We assessed the effect of supplementation on prevalence of open neural tube defects in the province of Ontario. Among 336 963 women who underwent maternal serum screening over 77 months, the prevalence of open neural tube defects declined from 1.13 per 1000 pregnancies before fortification to 0.58 per 1000 pregnancies thereafter (prevalence ratio 0.52, 95% CI 0.40-0.67, p<0.0001). At a population level, folic acid food fortification is associated with a pronounced reduction in open neural tube defects.

Identity-by-descent filtering of exome sequence data identifies PIGV mutations in hyperphosphatasia mental retardation syndrome

Hyperphosphatasia mental retardation (HPMR) syndrome is an autosomal recessive form of mental retardation with distinct facial features and elevated serum alkaline phosphatase. We performed whole-exome sequencing in three siblings of a nonconsanguineous union with HPMR and performed computational inference of regions identical by descent in all siblings to establish PIGV, encoding a member of the GPI-anchor biosynthesis pathway, as the gene mutated in HPMR. We identified homozygous or compound heterozygous mutations in PIGV in three additional families.

Familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. Effects of mutant gene dosage on phenotype.

Neonatal severe hyperparathyroidism is a rare life-threatening disorder characterized by very high serum calcium concentrations (> 15 mg/dl). Many cases have occurred in families with familial hypocalciuric hypercalcemia, a benign condition transmitted as a dominant trait. Among several hypothesized relationships between the two syndromes is the suggestion that neonatal severe hyperparathyroidism is the homozygous form of familial hypocalciuric hypercalcemia. To test this hypothesis, we refined the map location of the gene responsible for familial hypocalciuric hypercalcemia on chromosome 3q. Analyses in 11 families defined marker loci closely linked to the gene responsible for familial hypocalciuric hypercalcemia. These loci were then analyzed in four families with parental consanguinity and offspring with neonatal severe hyperparathyroidism. Each individual who was homozygous for loci that are closely linked to the gene responsible for familial hypocalciuric hypercalcemia had neonatal severe hyperparathyroidism. The calculated odds of linkage between these disorders of > 350,000:1 (lod score = 5.56). We conclude that dosage of the gene defect accounts for these widely disparate clinical phenotypes; a single defective allele causes familial hypocalciuric hypercalcemia, while two defective alleles causes neonatal severe hyperparathyroidism.

Mutations of the calcium-sensing receptor (CASR) in familial hypocalciuric hypercalcemia, neonatal severe hyperparathyroidism, and autosomal dominant hypocalcemia.

The calcium‐sensing receptor (CASR) is a plasma membrane G protein coupled receptor that is expressed in the parathyroid hormone (PTH) producing chief cells of the parathyroid gland and the cells lining the kidney tubule. By virtue of its ability to sense small changes in circulating calcium concentration ([Ca2+]o) and to couple this information to intracellular signaling pathways that modify PTH secretion or renal cation handling, the CASR plays an essential role in maintaining mineral ion homeostasis. Inherited abnormalities of the CASR gene located on chromosome 3p13.3‐21 can cause either hypercalcemia or hypocalcemia depending upon whether they are inactivating or activating, respectively. Heterozygous loss‐of‐function mutations give rise to familial (benign) hypocalciuric hypercalcemia (FHH) in which the lifelong hypercalcemia is asymptomatic. The homozygous condition manifests itself as neonatal severe hyperparathyroidism (NSHPT), a rare disorder characterized by extreme hypercalcemia and the bony changes of hyperparathyroidism which occur in infancy. The disorder autosomal dominant hypocalcemia (ADH) is due to gain‐of‐function mutations in the CASR gene. ADH may be asymptomatic or present with neonatal or childhood seizures. A common polymorphism in the intracellular tail of the CASR, Ala to Ser at position 986, has a modest effect on the serum calcium concentration in healthy individuals. Hum Mutat 16:281–296, 2000.

Determinants of Peak Bone Mass: Clinical and Genetic Analyses in a Young Female Canadian Cohort

Peak bone mass has been shown to be a significant predictor of risk for osteoporosis. Previous studies have demonstrated that skeletal mass accumulation is under strong genetic control, and efforts have been made to identify candidate loci. Determinants of peak bone mass also include diet, physical activity, hormonal status, and other clinical factors. The overall contribution of these factors, genetic and nongenetic, and their interaction in determining peak bone density status have not been delineated. Six hundred and seventy‐seven healthy unrelated Caucasian women ages 18–35 years were assessed. A detailed, standardized interview was conducted to evaluate lifestyle factors, menstrual and reproductive history, medical conditions, medication use, and family history of osteoporosis. Bone mineral density (BMD) was measured at the lumbar spine (L2–L4) and the femoral neck (hip) using dual‐energy X‐ray absorptiometry. Genotyping of the vitamin D receptor (VDR) locus at three polymorphic sites (BsmI, ApaI, and TaqI) was performed. In bivariate analyses, BMD at the lumbar spine and hip was positively correlated with weight, height, body mass index (BMI), and level of physical activity, both now and during adolescence, but negatively correlated with a family history of osteoporosis. Hip, but not spine BMD, correlated positively with dietary intake of calcium, and negatively with amenorrhea of more than 3 months, with caffeine intake, and with age. Spine, but not hip BMD, correlated positively with age and with number of pregnancies. VDR haplotype demonstrated significant associations with BMD at the hip, level of physical activity currently, and BMI. In multivariate analysis, independent predictors of greater BMD (at the hip or spine) were: age (younger for the hip, older for the spine), greater body weight, greater height (hip only), higher level of physical activity now and during adolescence, no family history of osteoporosis, and VDR genotype (hip only). Weight, age, level of physical activity, and family history are independent predictors of peak BMD. Of these factors, weight accounts for over half the explained variability in BMD. VDR alleles are significant independent predictors of peak femoral neck, but not lumbar spine BMD, even after adjusting for family history of osteoporosis, weight, age, and exercise. However, the overall contribution of this genetic determinant is modest. Taken together, these factors explained ∼17% and 21% of the variability in peak spine and hip BMD, respectively, in our cohort. Future research should be aimed at further evaluation of genetic determinants of BMD. Most importantly, understanding the critical interactive nature between genes and the environment will facilitate development of targeted strategies directed at modifying lifestyle factors as well as earlier intervention in the most susceptible individuals.

Recommended evaluation of adrenal incidentalomas is costly, has high false-positive rates and confers a risk of fatal cancer that is similar to the risk of the adrenal lesion becoming malignant; time for a rethink?

OBJECTIVE To assess the performance of current clinical recommendations for the evaluation of an adrenal incidentaloma. DESIGN AND METHODS LITERATURE REVIEW: Electronic databases (Pubmed, Ovid and citation searches from key articles) from 1980 to 2008 were searched. Eligible studies were those deemed most applicable to the clinical scenario of a patient referred to an endocrinologist for assessment of an incidentally detected adrenal mass. Surgical series, histopathological series and oncological series were reviewed and most were excluded. RESULTS The prevalence of functional and malignant lesions presenting as adrenal incidentaloma was similar to that quoted in most reviews, other than a lower incidence of adrenal carcinoma (1.9 vs 4.7%) and metastases (0.7 vs 2.3%). The development of functionality or malignancy during follow-up was rare (<1% becoming functional and 0.2% becoming malignant). During follow-up, false-positive rates of the recommended investigations are typically 50 times greater than true positive rates. The average recommended computed tomography (CT) scan follow-up exposes each patient to 23 mSv of ionising radiation, equating to a 1 in 430 to 2170 chance of causing fatal cancer. This is similar to the chance of developing adrenal malignancy during 3-year follow-up of adrenal incidentaloma. CONCLUSION Current recommendations for evaluation of adrenal incidentaloma are likely to result in significant costs, both financial and emotional, due to high false-positive rates. The dose of radiation involved in currently recommended CT scan follow-up confers a risk of fatal cancer that is similar to the risk of the adrenal becoming malignant. This argues for a review of current guidelines.

A986S polymorphism of the calcium-sensing receptor and circulating calcium concentrations

BACKGROUND The regulation of extracellular calcium concentration by parathyroid hormone is mediated by a calcium-sensing, G-protein-coupled cell-surface receptor (CASR). Mutations of the CASR gene alter the set-point for extracellular ionised calcium [Ca2+]o and cause familial hypercalcaemia or hypocalcaemia. The CASR missense polymorphism, A986S, is common in the general population and is, therefore, a prime candidate as a genetic determinant of extracellular calcium concentration. METHODS We genotyped the CASR A986S variant (S allele frequency of 16.3%) in 163 healthy adult women and tested samples of their serum for total calcium, albumin, total protein, creatinine, phosphate, pH, and parathyroid hormone. A prospectively generated, random subset of 84 of these women provided a whole blood sample for assay of [Ca2+]o. FINDINGS The A986S genotype showed no association with total serum concentration of calcium, until corrected for albumin. In a multivariate regression model, biochemical and genetic variables accounted for 74% of the total variation in calcium. The significant predictors of serum calcium were: albumin (p<0.001), phosphate (p=0.02), parathyroid hormone (p=0.007), pH (p=0.001), and A986S genotype (p=0.009). Fasting whole-blood [Ca2+]o also showed an independent positive association with the 986S variant (p=0.013). INTERPRETATION The CASR A986S variant has a significant effect on extracellular calcium. The CASR A986S polymorphism is a likely candidate locus for genetic predisposition to various bone and mineral disorders in which extracellular calcium concentrations have a prominent part.

Founder BRCA1 and BRCA2 mutations in French Canadian breast and ovarian cancer families

We have identified four mutations in each of the breast cancer-susceptibility genes, BRCA1 and BRCA2, in French Canadian breast cancer and breast/ovarian cancer families from Quebec. To identify founder effects, we examined independently ascertained French Canadian cancer families for the distribution of these eight mutations. Mutations were found in 41 of 97 families. Six of eight mutations were observed at least twice. The BRCA1 C4446T mutation was the most common mutation found, followed by the BRCA2 8765delAG mutation. Together, these mutations were found in 28 of 41 families identified to have a mutation. The odds of detection of any of the four BRCA1 mutations was 18.7x greater if one or more cases of ovarian cancer were also present in the family. The odds of detection of any of the four BRCA2 mutations was 5.3x greater if there were at least five cases of breast cancer in the family. Interestingly, the presence of a breast cancer case <36 years of age was strongly predictive of the presence of any of the eight mutations screened. Carriers of the same mutation, from different families, shared similar haplotypes, indicating that the mutant alleles were likely to be identical by descent for a mutation in the founder population. The identification of common BRCA1 and BRCA2 mutations will facilitate carrier detection in French Canadian breast cancer and breast/ovarian cancer families.

Vitamin B12 and the risk of neural tube defects in a folic-acid-fortified population.

Background: Low maternal vitamin B12 status may be a risk factor for neural tube defects (NTDs). Prior studies used relatively insensitive measures of B12, did not adjust for folate levels, and were conducted in countries without folic acid food fortification. In Canada, flour has been fortified with folic acid since mid-1997. Methods: We completed a population-based case–control study in Ontario. We measured serum holotranscobalamin (holoTC), a sensitive indicator of B12 status, at 15 to 20 weeks’ gestation. There were 89 women with an NTD and 422 unaffected pregnant controls. A low serum holoTC was defined as less than 55.3 pmol/L, the bottom quartile value in the controls. Results: The geometric mean serum holoTC levels were 67.8 pmol/L in cases and 81.2 pmol/L in controls. There was a trend of increasing risk with lower levels of holoTC, reaching an adjusted odds ratio of 2.9 (95% confidence interval = 1.2–6.9) when comparing the lowest versus highest quartile. Conclusions: There was almost a tripling in the risk for NTD in the presence of low maternal B12 status, measured by holoTC. The benefits of adding synthetic B12 to current recommendations for periconceptional folic acid tablet supplements or folic-acid-fortified foods need to be considered. It remains to be determined what fraction of NTD cases in a universally folate-fortified environment might be prevented by higher periconceptional intake of B12.