Relationships of serum free thyroxine and erythrocyte measures in euthyroid HFE C282Y homozygotes and control subjects: the HEIRS study.

Hemoglobin (Hb) levels and mean corpuscular volume (MCV) are abnormal in some persons with hemochromatosis or thyroid disorders. We sought to determine whether serum free thyroxine (T4) affects erythrocyte measures in euthyroid adults with or without C282Y homozygosity. We evaluated 488 white HFE C282Y homozygotes and controls (no HFE C282Y or H63D; normal serum iron measures) identified in screening; we excluded those with thyroid disorders, anemia, erythrocytosis, or serum ferritin (SF) <34 pmol/l. In the remaining 141 C282Y homozygotes and 243 controls, we evaluated correlations of log(10) free T4 with Hb, RBC, MCV, and red blood cell distribution width (RDW). C282Y homozygotes had lower mean age, higher mean Hb, MCV, and log(10) SF, and lower mean RBC and RDW than controls; mean log(10) free T4 did not differ significantly. In HFE C282Y homozygotes, there was no significant correlation of log(10) T4 with erythrocyte measures. In controls, there was a positive correlation of log(10) T4 with Hb (P = 0.0096) and a negative correlation with RDW (P = 0.0286). Among euthyroid white adults without iron deficiency, there are significant correlations of log(10) free T4 with Hb and RDW in controls, but not in HFE C282Y homozygotes.

Influence of CYP2C9 and VKORC1 on warfarin response during initiation of therapy.

BACKGROUND: Although multiple reports have documented the influence of CYP2C9 and VKORC1 variants on warfarin dose, risk of over-anticoagulation and hemorrhage, their influence on anticoagulation maintenance and individual proportion of time spent in target INR range (PPTR) is limited. Moreover the potential benefit of genotype-guided dosing implemented after initiation of therapy in a racially diverse population has not been explored. Herein we present the influence of CYP2C9 and VKORC1 C1173T on warfarin response during the first 30 days of therapy. METHODS: Warfarin dose was empirically determined in 250 African Americans 271 European Americans. The influence of CYP2C9 and VKORC1 on rate of INR increase, anticoagulation maintenance, risk of over-anticoagulation, and change in dose over 30 days was evaluated after adjustment for socio-demographic, lifestyle and clinical factors. Possession of variant VKORC1 (+/- variant CYP2C9) genotype was associated with a more rapid attainment of target INR and higher frequency of dose adjustments. Patients possessing variant genotypes spent less time in target range. However adjustment for rate of INR increase rendered the association non-significant. European Americans (but not African Americans) possessing variant VKORC1 (+/- variant CYP2C9) genotype had a higher risk of over-anticoagulation. Neither CYP2C9 nor VKORC1 influenced the risk of minor hemorrhage. CYP2C9 and VKORC1 explained 6.3% of the variance in dose change over the first 30 days of therapy demonstrating that the usefulness of genotype-guided dosing may extend beyond first day of therapy. CONCLUSION: The benefit of genotype-based dose prediction may extend beyond first few days of therapy. Whether genotype-guided dosing will decrease the risk of over-anticoagulation, improve anticoagulation control and most importantly improve outcomes for chronic warfarin users remains to be proven.

Serial serum ferritin measurements in untreated HFE C282Y homozygotes in the Hemochromatosis and Iron Overload Screening Study.

Hemochromatosis has often been associated with progressive iron overload, but the natural history of iron accumulation in untreated C282Y homozygotes has been reported infrequently. The Hemochromatosis and Iron Overload Screening (HEIRS) Study screened 101 168 primary care participants for iron overload using transferrin saturation, unbound iron-binding capacity, Serum ferritin (SF), and HFE C282Y and H63D genotyping. SF was measured at initial screening (IS) and again when selected participants returned for a clinical examination (CE). The change in SF over the observation period (defined as ferritin rate of change) was analyzed according to age, gender, initial SF, initial SF/age, transferrin saturation, and iron removed by phlebotomy in C282Y homozygotes. Seventy-four male and 133 female untreated C282Y homozygotes were observed over a median of 112 days (34-924 days) between IS and CE. In men, SF increased in 54% and decreased in 46%. In women, SF increased in 50% and decreased in 50%. The significant variables affecting the SF rate were initial log SF (P = 0.0027) and transferrin saturation (P < 0.0001). Male C282Y homozygotes with higher SF rates (n = 27, upper 50th percentile) had significantly greater iron removed by phlebotomy (mean 4.93 g, range 1.0-17 g) than those with lower SF rates (n = 26, lower 50th percentile) (mean 2.6 g, 0.42-7.1, P < 0.05). SF was as likely to decrease as increase in untreated C282Y homozygotes over this relatively brief observation period. Incremental increases in SF are not inevitable in untreated C282Y homozygotes.

Influence of CYP2C9 and VKORC1 1173C/T genotype on the risk of hemorrhagic complications in African-American and European-American patients on warfarin.

The association of CYP2C9 and VKORC1 1173C/T genotype and risk of hemorrhage among African Americans and European Americans is presented. This association was evaluated using Cox proportional hazard regression with adjustment for demographics, comorbidity, and time-varying covariates. Forty-four major and 203 minor hemorrhages occurred over 555 person-years among 446 patients (60.6+/-15.6 years, 50% men, 227 African Americans). The variant CYP2C9 genotype conferred an increased risk for major (hazard ratio (HR) 3.0; 95% confidence interval (CI): 1.1-8.0) but not minor (HR 1.3; 95% CI: 0.8-2.1) hemorrhage. The risk of major hemorrhage was 5.3-fold (95% CI: 0.4-64.0) higher before stabilization of therapy, 2.2-fold (95% CI: 0.7-6.5) after stabilization, and 2.4-fold (95% CI: 0.8-7.4) during all periods when anticoagulation was not stable. The variant VKORC1 1173C/T genotype did not confer a significant increase in risk for major (HR 1.7; 95% CI: 0.7-4.4) or minor (HR 0.8; 95% CI: 0.5-1.3) hemorrhage. The variant CYP2C9 genotype is associated with an increased risk of major hemorrhage, which persists even after stabilization of therapy.

DMPK-associated myotonic dystrophy and CTG repeats in Alabama African Americans.

Myotonic dystrophy type 1 (DM1) is a result of a CTG expansion in the 3'-untranslated region of the DMPK gene. DM1 is rare among African blacks who have fewer large CTG repeats in the normal range than other racial/ethnic groups. Neither the prevalence of DM1 nor the relationship of CTG expansion to clinical status in African Americans (AAs) is well documented. We describe two AA brothers with DM1, each of whom had CTG repeats of 5/639; their father was reported to have DM1 and had CTG repeats of 5/60. Other family members had CTG repeats of 5-14. An unrelated AA patient from a second kinship also had DM1; an analysis revealed CTG repeats of 27/191. In 161 Alabama AA control subjects, we observed 18 CTG alleles from 5 to 28 repeats; the most common allele had five CTG repeats. The frequency of CTG repeats >or=15 were greater (p < 0.0003) in Pygmy, Amhara Ethiopian, Ashkenazi Jewish, North African Jewish, Israeli Muslim Arab, European white, and Japanese populations than in the Alabama AA population. These data suggest that the risk for DM1 in AAs is intermediate between that of African blacks and whites of European descent.

A genome-wide linkage scan for iron phenotype quantitative trait loci: the HEIRS Family Study.

Iron overload phenotypes in persons with and without hemochromatosis are variable. To investigate this further, probands with hemochromatosis or evidence of elevated iron stores and their family members were recruited for a genome-wide linkage scan to identify potential quantitative trait loci (QTL) that contribute to variation in transferrin saturation (TS), unsaturated iron-binding capacity (UIBC), and serum ferritin (SF). Genotyping utilized 402 microsatellite markers with average spacing of 9 cM. A total of 943 individuals, 64% Caucasian, were evaluated from 174 families. After adjusting for age, gender, and race/ethnicity, there was evidence for linkage of UIBC to chromosome 4q logarithm of the odds (LOD) = 2.08, p = 0.001) and of UIBC (LOD = 9.52), TS (LOD = 4.78), and SF (LOD = 2.75) to the chromosome 6p region containing HFE (each p < 0.0001). After adjustments for HFE genotype and other covariates, there was evidence of linkage of SF to chromosome 16p (LOD = 2.63, p = 0.0007) and of UIBC to chromosome 5q (LOD = 2.12, p = 0.002) and to chromosome 17q (LOD = 2.19, p = 0.002). We conclude that these regions should be considered for fine mapping studies to identify QTL that contribute to variation in SF and UIBC.

Racial differences in the prevalence of Factor V Leiden mutation among patients on chronic warfarin therapy.

We report the prevalence of Factor V Leiden (FVL) in European American and African American patients on warfarin therapy residing in Alabama. METHODS.: Detailed history was obtained and FVL genotype was determined for 288 patients enrolled in a prospective cohort: Pharmacogenetic Optimization of Anticoagulation Therapy. Racial differences in genotype frequency were assessed by the Chi-square statistics and HWE assumptions by G-statistics. Race-specific analysis for the association between site of thromboembolism and the presence of FVL mutation was assessed using logistic regression. RESULTS.: The overall heterozygote (GA genotype) frequency was 4.9%. No patient was found to be homozygous (AA) for the variant allele. The prevalence of GA was higher in European American (8.6%) compared to African American (1.4%) patients (p=0.004). The FVL genotype frequency was significantly different across race for venous thromboembolic events (p=0.014) but not for arterial thromboembolic events (p=0.20). Multivariable race-specific analysis highlights the contribution of FVL mutation to the risk of venous thromboembolic events in European American (p=0.03) but not in African American patients (p=0.95). European American patients with the GA mutation were approximately 6.3 times more likely to have experienced a venous, rather than arterial thromboembolic event. CONCLUSION.: In Alabama, among patients on warfarin, the GA genotype is more prevalent in European Americans compared to African Americans. In European Americans, but not in African Americans, the GA genotype was more prevalent in patients with venous compared to arterial thromboembolic events.

Initial screening transferrin saturation values, serum ferritin concentrations, and HFE genotypes in Native Americans and whites in the Hemochromatosis and Iron Overload Screening Study.

We compared initial screening transferrin saturation (TfSat) and serum ferritin (SF) phenotypes and HFE C282Y and H63D genotypes of 645 Native American and 43,453 white Hemochromatosis and Iron Overload Screening Study participants who did not report a previous diagnosis of hemochromatosis or iron overload. Elevated measurements were defined as TfSat >50% in men and >45% in women and SF >300 ng/ml in men and >200 ng/ml in women. Mean TfSat was 31% in Native American men and 32% in white men (p = 0.0337) and 25% in Native American women and 27% in white women (p < 0.0001). Mean SF was 153 microg/l in Native American and 151 microg/l in white men (p = 0.8256); mean SF was 55 microg/l in Native American women and 63 microg/l in white women (p = 0.0015). The C282Y allele frequency was 0.0340 in Native Americans and 0.0683 in whites (p < 0.0001). The H63D allele frequency was 0.1150 in Native Americans and 0.1532 in whites (p = 0.0001). We conclude that the screening TfSat and SF phenotypes of Native Americans are similar to those of whites. The allele frequencies of HFE C282Y and H63D are significantly lower in Native Americans than in whites.

Prevalence and risk factors of microalbuminuria in a cohort of African-American women with gestational diabetes.

OBJECTIVE: To study the prevalence of microalbuminuria (MA) in African-American women with a history of gestational diabetes (GDM) who are at high risk for insulin resistance and renal dysfunction and to study MA's relation to insulin resistance, type 2 diabetes, and hypertension. RESEARCH DESIGN AND METHODS: MA was assessed using 24-h, timed, and/or random urine samples in a cross-sectional sample (n = 289) from a cohort of African-American women with a history of GDM and followed for a median of 11 years (range 3.0-18.4) since their diabetic pregnancy. Subjects with a urine albumin excretion rate of 30-300 g/24 h or 30-300 microg/mg creatinine in a random sample were classified as having MA if two of three samples over a 3- to 6-month period were positive. These women were evaluated for family history of diabetes, smoking and alcohol use, BMI, diabetes, hypertension, and lipid abnormalities. Insulin sensitivity was determined using the homeostasis model assessment (HOMA) estimates, which used fasting insulin and glucose measurements obtained at the same time as the MA urine sample. RESULTS: At MA assessment, the women ranged in age from 22 to 57 years, with a median of 39 years. The overall prevalence of MA was 20%; 36% in those with diabetes. Those women with MA had higher rates of diabetes (63.8 vs. 28.6%, odds ratio [OR] = 4.4, P < 0.05), hypertension (82.8 vs. 42.9%, OR = 6.4, P < 0.05), and family history of diabetes (85.7 vs. 61.7%, OR = 3.7, P < 0.05). The proportion of subjects with MA with a family history of hypertension was nonsignificantly increased (92.9 vs. 82.4%). Subjects with MA were more obese (BMI 37.2 +/- 8.9 vs. 34.4 +/- 8.6 kg/m(2)) and had higher levels of HbA(1c) (8.8 +/- 3.3 vs. 6.6 +/- 1.8%, P < 0.001) and systolic (144.3 +/- 25.9 vs. 122.8 +/- 17.2 mmHg, P < 0.0001) and diastolic (95.1 +/- 15.4 vs. 82.5 +/- 11.9 mmHg, P < 0.0001) blood pressures. Lipid fractions were similar in those with and without MA. Although fasting glucose was much higher in subjects with MA (10.3 +/- 5.8 vs. 7.1 +/- 4.2 mmol/l, P = 0.0002), insulin levels were not significantly higher in subjects with MA (17.4 +/- 21.2 vs. 15.2 +/- 12.4 pmol/l). Insulin sensitivity, as measured using log HOMA, was similar (1.5 +/- 0.6 vs. 1.6 +/- 0.6) in women with and without MA, respectively. Multivariable logistic regression analyses indicated that HbA(1c), OR = 1.16 (1.07, 1.27), and systolic blood pressure, OR = 1.27 (1.14, 1.41), were independent risk factors for MA. In those with diabetes, the subjects with MA had higher rates of hypertension-83.8 vs. 56.1%, OR = 4.1 (1.5, 11.10)-which was reflected by their higher systolic and diastolic blood pressures, 146.1 mmHg (P = 0.001) and 94.8 mmHg (P = 0.002), respectively, and lower levels of VLDL (0.45 +/- 0.22 vs. 0.61 +/- 0.33 mmol/l, P = 0.021). In the multivariable analyses of those with diabetes, the two independent risk factors for MA were similar: HbA(1c), OR = 1.13 (1.01, 1.28), and systolic blood pressure, OR = 1.21 (1.04, 1.41). CONCLUSIONS: African-American women with a history of GDM have one of the highest rates for MA. Presence of MA was not associated with insulin resistance but was significantly independently associated with HbA(1c) levels and hypertension. These results, taken in context of the literature, suggest that hypertension and glucose intolerance, in part, influence MA through different mechanisms. Because of the high prevalence of MA in this population and MA's relation to all-cause and cardiovascular mortality, screening for MA should be considered.

A rapid PCR-SSP assay for the hemochromatosis-associated Tyr250Stop mutation in the TFR2 gene.

Several genes associated with hemochromatosis and primary iron overload have been identified. Mutations in the HFE gene have been detected in 60-100% of hemochromatosis patients of northern, central, and western European descent, although the frequencies of these mutations vary among racial and ethnic groups. Recently, a mutation in the gene encoding transferrin receptor-2 (exon 6, nucleotide 750 C --> G; Y250X) was detected by a PCR-restriction fragment length polymorphism (RFLP) method in Sicilians with hemochromatosis. We describe a modification of the original assay in which the sequence-specific priming PCR assay does not require the use of restriction endonuclease. The modified assay is robust and cost-efficient, and may be more useful for large-scale population studies because it can be performed rapidly on DNA extracted from buccal swabs.

Inheritance of two HFE mutations in African Americans: cases with hemochromatosis phenotypes and estimates of hemochromatosis phenotype frequency.

PURPOSE: Two unrelated African Americans had hemochromatosis phenotypes and genotypes. We sought to identify origins of their HFE mutations and estimate frequencies of similar cases. METHODS: HFE and HLA genotyping were performed in index cases and family members. HFE genotypes of 1,373 African American controls in five regions were tabulated. RESULTS: Index cases had C282Y/C282Y and C282Y/H63D, respectively; each corresponding Ch6p was likely of Caucasian origin. In controls, frequencies of hemochromatosis-associated genotypes were as follows: C282Y/C282Y, 0.00011; C282Y/H63D, 0.00067; and H63D/H63D, 0.00101. CONCLUSIONS: Penetrance-adjusted estimates indicate that approximately 9 African Americans per 100,000 have a hemochromatosis phenotype and two common HFE mutations. Hemochromatosis-associated genotype frequencies varied 11.7-fold across regions.

Transferrin receptor-2 (TFR2) mutation Y250X in Alabama Caucasian and African American subjects with and without primary iron overload.

Most cases of hemochromatosis are associated with mutations of the HFE gene on Ch6p. In southern Italy and central Alabama, the percentages of patients with hemochromatosis who have "atypical" HFE genotypes (defined as lack of C282Y homozygosity, C282Y/H63D compound heterozygosity, or H63D homozygosity) are relatively great. A mutation of the transferrin receptor-2 gene (TFR2; exon 6, nt 750 C --> G, replaces TAC with stop signal TAG; Y250X) on Ch7q22 was recently identified in two Sicilian families with HFE mutation-negative hemochromatosis. We wanted to estimate the frequency of this mutation in persons from central Alabama. We evaluated Caucasian hemochromatosis probands with atypical HFE genotypes and African Americans with primary iron overload. We also studied control Caucasians, including persons of southern Italian/Sicilian heritage, and control African Americans. Analysis of genomic DNA was performed using a PCR-sequence-specific priming assay and positive control specimens from Sicilian hemochromatosis subjects heterozygous and homozygous for Y250X. Among Alabama subjects, this allele was not detected in 113 Caucasians, including 21 hemochromatosis probands with atypical HFE genotypes and 92 normal control subjects (including 27 of southern Italian/Sicilian descent). In African Americans, Y250X was not detected in 20 index cases with primary iron overload or in 274 unrelated control subjects. We conclude that Y250X is uncommon in Caucasians with hemochromatosis associated with atypical HFE genotypes, in African Americans with primary iron overload, and in the general Caucasian and African American population subgroups in central Alabama.

Investigation of association of 13 polymorphisms in eight genes in southeastern African American Alzheimer disease patients as compared to age-matched controls.

Alzheimer disease (AD) is an emotionally devastating and exceptionally costly disease. Apolipoprotein E (APOE) is a major risk factor gene for AD regardless of age of onset or family history. However, this association may not be as strong or consistent in ethnic groups such as African Americans, raising the possibility of other modifier gene(s). In a group of African American AD patients, a significantly increased risk of AD was associated with two E4 alleles (OR = 5.6; 95% CI = 1.5-21.0) or one E4 allele (OR = 2.5; 95% CI = 1.3-5.0) when compared to E3/E3 genotype, and there was a significant lowering of age of onset for affecteds with E4/E4 genotype as compared to one E2 allele (P = 0.02) or all others (P = 0.03). We also found a significant increase in age of onset with the -308 #2 (A) allele of TNF when compared to AD cases with no #2 allele. A significant increase in age was also demonstrated with the #2 allele (99 base pairs) of the microsatellite TNFa, located approximately 10.5 kb upstream of TNF. When these two alleles were combined with the TNF -238G (#1) allele to give a haplotype, the significant increase in age was still demonstrated. Polymorphisms in the APOE promoter and six other candidate genes did not appear to demonstrate any significant association with our African American AD patients. Our results confirm the established association of APOE4 to AD observed in several ethnic groups, including African Americans. In addition, TNF appears to have some modifying effect in AD, primarily on age of onset, or it could be in linkage disequilibrium with a modifier locus nearby.

Hemochromatosis and iron therapy of Restless Legs Syndrome.

Restless legs syndrome (RLS) occurs in some persons with iron deficiency, and some persons with RLS benefit from oral iron therapy. Approximately one in 200 persons of northern European ancestry have hemochromatosis attributable to inheritance of two common mutations of the hemochromatosis-associated HFE gene on chromosome 6. We evaluated and treated a 46-year-old man with RLS who was diagnosed as having hemochromatosis after he developed new symptoms associated with taking iron therapy for RLS. He had transferrin saturation 88%, serum ferritin 658 ng/ml, and C282Y homozygosity. Therapeutic phlebotomy of one unit of blood (450-500 ml) weekly (total 24 units) relieved his non-RLS symptoms, caused RLS symptoms to occur more frequently, and was associated with transient fatigue and mild dependent edema. His sister, who also has RLS, was subsequently diagnosed as having hemochromatosis. We conclude that serum transferrin saturation and ferritin levels should be measured before initiation of iron therapy of RLS. Patients with a history of iron deficiency or low serum iron parameters should undergo evaluation for iron deficiency; patients who have histories suggestive of hemochromatosis or iron overload or elevated pre-treatment transferrin saturation or serum ferritin levels should undergo evaluation to determine the cause of these abnormalities before they are treated with iron. In all persons with RLS treated with oral iron, serum iron parameters should be re-measured once or twice yearly during therapy.

HFE genotype frequencies in consecutive reference laboratory specimens: comparisons among referral sources and association with initial diagnosis.

We quantified HFE genotype frequencies in specimens submitted by physicians grouped by specialty and determined associations of genotypes with initial diagnosis based on phenotyping in patients evaluated at an iron disorders center. Of 526 specimens (519 from Alabama), these "typical" hemochromatosis-associated genotypes were detected: 85 C282Y/C282Y, 50 C282Y/H63D, and 27 H63D/H63D. Respective frequencies of C282Y/C282Y in specimens from an iron disorders center (n = 156), gastroenterologists (n = 147), hematologists/medical oncologists (n = 85), liver transplant surgeons (n = 11), endocrinologists and rheumatologists (n = 9), and "other sources" (n = 7) were greater (p < 0.05) than in population controls. In 44 patients from an iron disorders center initially diagnosed as "presumed hemochromatosis," 27 (61.4%) had C282Y/C282Y, 10 (22.7%) had C282Y/H63D, and 3 (6.8%) had H63D/H63D. C282Y/C282Y was not detected in 48 patients with "abnormality probably not an iron overload disorder." A total of 20.5% of 44 family members of patients had "typical" hemochromatosis-associated HFE genotypes (7.0% controls; p = 0.02). We conclude that most physicians who submitted specimens identify patients by phenotyping who have greater frequencies of "typical" hemochromatosis-associated HFE genotypes than controls, and that HFE mutation testing is useful in detecting hemochromatosis in family members of persons with hemochromatosis or iron overload.

A primer for predicting risk of disease in HFE-linked hemochromatosis.

Since the discovery of the hemochromatosis gene (HFE) in 1996, there has been increasing interest in diagnostic testing for the C282Y and H63D mutations. The high frequency of these two alleles and their incomplete penetrance in homozygotes and compound heterozygotes make genetic counseling for hemochromatosis different from some other autosomal recessive conditions in that parents and children may also be at risk for iron overload, while homozygotes may remain asymptomatic. We provide a guideline for genetic counseling in HFE-linked hemochromatosis based on the genetic probability of inheriting HFE mutations and known information about expression of iron overload in various HFE genotypes. Genetic probabilities were based on allele frequencies derived from large population studies and Hardy-Weinberg equilibrium estimates. Expression of iron overload in those of various genotypes was based on available estimates of serum ferritin from population screening studies. Estimates for the likelihood of clinical iron overload requiring follow-up screening or treatment are provided by gender and genotype. The probability of inheriting HFE mutations and developing iron overload can be estimated in family members of a proband with HFE mutations. Many C282Y homozygotes will not have clinical iron overload. The risk is highest in men and their C282Y homozygous brothers and significantly lower in homozygous women. Iron overload is uncommon in compound heterozygotes and H63D homozygotes.

HFE mutations in African-American women with non-insulin-dependent diabetes mellitus.

The aim of this study was to compare the frequencies of HFE mutations in African-American women with non-insulin-dependent diabetes mellitus (NIDDM) to that of controls and to determine whether these mutations are associated with NIDDM and iron overload. We studied 167 African-American women with NIDDM. The 71 non-diabetic controls were African-American female controls. HLA-A and -B typing and HFE mutation analysis for C282Y and H63D alleles were performed using standard molecular genetic techniques. The frequencies of C282Y and H63D were not significantly different in NIDDM patients and controls. C282Y was observed in 0.59% of patients and 1.41% of controls. H63D was observed in 2.99% of patients and 3.08% of controls. All of the NIDDM patients who possessed either C282Y or H63D mutations had normal values of serum ferritin, serum iron and transferrin saturation. A woman who inherited C282Y also possessed HLA-A3, -B7 which is considered part of the ancestral haplotype containing the gene predisposing to hemochromatosis in Caucasians. The frequencies of C282Y and H63D vary in African Americans from different geographic regions of the United States; this variance can be explained by Caucasian admixture. Although most iron overload cases in African Americans bear more resemblance to cases of African iron overload than to those of Caucasian hemochromatosis, rare cases resembling Caucasian hemochromatosis have been observed in African Americans.

Association of a haplotype for tumor necrosis factor in siblings with late-onset Alzheimer disease: the NIMH Alzheimer Disease Genetics Initiative.

Tumor necrosis factor (TNF), a proinflammatory cytokine, may be involved in the pathogenesis of Alzheimer disease (AD) based on observations that senile plaques have been found to upregulate proinflammatory cytokines. Additionally, nonsteroidal anti-inflammatory drugs have been found to delay and prevent the onset of AD. A collaborative genome-wide scan for AD genes in 266 late-onset families implicated a 20 centimorgan region at chromosome 6p21.3 that includes the TNF gene. Three TNF polymorphisms, a -308 TNF promoter polymorphism, whose TNF2 allele is associated with autoimmune inflammatory diseases and strong transcriptional activity, the -238 TNF promoter polymorphism, and the microsatellite TNFa, whose 2 allele is associated with a high TNF secretion, were typed in 145 families consisting of 562 affected and unaffected siblings. These polymorphisms formed a haplotype, 2-1-2, respectively, that was significantly associated with AD (P = 0.005) using the sibling disequilibrium test. Singly, the TNFa2 allele was also significantly associated (P = 0.04) with AD in these 145 families. This TNF association with AD lends further support for an inflammatory process in the pathogenesis of AD. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:823-830, 2000.

Population screening for hemochromatosis: has the time finally come?

Hemochromatosis refers to a group of common heritable disorders among Western Caucasians which increase susceptibility for development of iron overload and its complications. These consequences are preventable by early detection and simple, relatively inexpensive treatment. Screening of appropriate populations to detect hemochromatosis before iron overload occurs is both effective and cost-effective. The primary goal of screening should be the ongoing detection of persons with hemochromatosis, especially healthy individuals whose risk to develop iron overload is great, in a context that provides appropriate preventive treatment, education, and counseling. Although related issues warrant further study, implementation of well-designed screening programs for hemochromatosis should not be delayed.