Corwin Q. Edwards

Prevalence of Hemochromatosis among 11,065 Presumably Healthy Blood Donors

There is evidence that iron loading and organ damage can be prevented in patients with hemochromatosis if prophylactic phlebotomy is employed early in the disease--findings emphasizing the importance of early detection before clinical signs occur. This study was designed to determine the efficacy of transferrin saturation as a screening tool for hemochromatosis and to assess the frequency of homozygosity for the HLA-linked hemochromatosis gene in a healthy population. We screened 11,065 presumably healthy blood donors (5840 men and 5225 women). Donors with transferrin saturations of 62 percent or more after an overnight fast were considered potential homozygotes and were asked to undergo liver biopsy and pedigree analysis. The frequency of values for transferrin saturation of 62 or higher in men was 0.008 and in women 0.003. Thirty-eight persons with values higher than 62 were studied in detail; 35 underwent liver biopsy. Liver iron stores ranged from normal to markedly increased. Twelve siblings with an identical HLA match to a proband underwent liver biopsy, and 11 had increased liver iron stores. According to likelihood analysis of the pedigrees, 26 of the 38 probands were homozygotes, and 12 were heterozygotes. The estimated frequency of homozygosity was based on the data in men, because the threshold value of 62 for the transferrin saturation identified only half as many female homozygotes as expected. The frequency of homozygosity was 0.0045, corresponding to a gene frequency of 0.067. The value of population screening is demonstrated in these studies by the detection of homozygotes before clinical manifestations of hemochromatosis occur.

Iron overload in Africa. Interaction between a gene and dietary iron content.

BACKGROUND AND METHODS In contrast to hemochromatosis, which in white populations is inherited through a gene linked to the HLA locus, iron overload in sub-Saharan Africa is believed to result solely from increased dietary iron derived from traditional home-brewed beer. To examine the hypothesis that African iron overload also involves a genetic factor, we used likelihood analysis to test for an interaction between a gene (the hypothesized iron-loading locus) and an environmental factor (increased dietary iron) that determines transferrin saturation and unsaturated iron-binding capacity. We studied 236 members of 36 African families chosen because they contained index subjects with iron overload. Linkage to the HLA region was tested with use of lod scores. RESULTS In the index subjects, increased iron was present in both hepatocytes and cells of the mononuclear-phagocyte system. Among family members with increased dietary iron due to the consumption of traditional beer, transferrin saturation in serum was distributed bimodally, with 56 normal values (less than 60 percent saturation) and 44 elevated values; the mean serum ferritin concentration was five times higher in the subjects with elevated transferrin saturation (P less than 0.005). The pedigree analysis provided evidence of both a genetic effect (P less than 0.005) and an effect of increased dietary iron (P less than 0.005) on transferrin saturation and unsaturated iron-binding capacity. In the most likely model, increased dietary iron raised the mean transferrin saturation from 30 to 81 percent and lowered the mean unsaturated iron-binding capacity from 38 to 13 mumol per liter in subjects heterozygous for the iron-loading locus. The hypothesis of tight linkage to HLA was rejected. CONCLUSIONS Iron overload in Africa may be caused by an interaction between the amount of dietary iron and a gene distinct from any HLA-linked gene.

Clinical and Biochemical Abnormalities in People Heterozygous for Hemochromatosis

BACKGROUND Ten percent of whites are heterozygous for the HLA-linked hemochromatosis mutation. We performed a cross-sectional analysis of 1058 genotyped heterozygotes to define the effects of age and sex on the phenotype. METHODS The heterozygous genotype was assigned to 505 male and 553 female members of 202 pedigrees, each with an HLA-typed homozygous proband. We measured serum iron, transferrin saturation, and ferritin in all heterozygotes and in 321 genetically normal subjects (unaffected family members or spouses of family members). Liver biopsies were performed in a subgroup of heterozygotes. RESULTS The mean serum iron concentrations and transferrin-saturation values were higher in heterozygotes than in normal subjects and did not increase with age. Initial transferrin-saturation levels exceeding the threshold associated with the homozygous genotype were found in 4 percent of male and 8 percent of female heterozygotes. The geometric mean serum ferritin concentration was higher in heterozygotes than in normal subjects and increased with age. Higher-than-normal values were found in 20 percent of male and 8 percent of female heterozygotes. The clinical and biochemical expression of hemochromatosis was more marked in heterozygotes with paternally transmitted mutations than in those with maternally transmitted mutations. Liver-biopsy abnormalities were generally associated with alcohol abuse, hepatitis, or porphyria cutanea tarda. CONCLUSIONS The phenotype of persons heterozygous for hemochromatosis differs from that of normal subjects, but complications due to iron overload alone in these heterozygotes are extremely rare.

Management of Hemochromatosis

Diagnosis and Initial Evaluation Diagnosis of Hemochromatosis Persons with hemochromatosis have an inherited propensity to absorb excess iron; most persons are of European origin and are homozygotes or compound heterozygotes for a mutant gene or genes on chromosome 6p [1, 2]. Hyperferremia and increased iron saturation of transferrin are essential attributes of hemochromatosis. A transferrin saturation of 60% or more for men and 50% or more for women on at least two occasions in the absence of other known causes of elevated transferrin saturation suggests the diagnosis of hemochromatosis [1, 2] and permits affected persons to be identified before iron overload develops. Normal or subnormal serum transferrin saturation values occur in unusual circumstances [3]. Many persons who have hemochromatosis without iron overload are children, young adults, and premenopausal women. Although iron overload often develops in patients with hemochromatosis, the demonstration of hepatic or systemic iron overload and associated complications is not needed to confirm the diagnosis (Table 1) [1, 2, 4]. Table 1. Evaluation of Patients with Hemochromatosis and Iron Overload Evaluation of Iron Overload Iron overload develops primarily because mechanisms to eliminate excess iron are limited. Many persons, particularly men, eventually develop severe iron overload. Women are at lower risk, partly because of iron losses during menstruation, childbirth, and lactation [1, 2]. The severity of iron overload is most often determined by measuring the serum ferritin level, although inflammation or cancer can elevate this level in the absence of iron overload. Approximately 90% of excess iron is retained in the liver. Therefore, many patients benefit from analysis of liver biopsy specimens to identify liver disease and to determine the presence or absence of cirrhosis, which directly affects prognosis. Biopsy specimens should be evaluated for iron by histochemical methods (Perls staining) and quantitative techniques (atomic absorption spectrometry) [4-7]. The quantity of iron removed by therapeutic phlebotomy is a valuable retrospective indicator of the severity of iron overload [8]. Radiologic imaging techniques are too insensitive for the evaluation of most young, asymptomatic persons with little or no excess hepatic iron [1, 2]. The hepatic iron index is useful in distinguishing persons who are homozygous for hemochromatosis from heterozygotes and persons with other hepatic disorders [5, 9]. Some patients have coincidental conditions that augment iron absorption and thus increase iron overload (for example, excessive dietary iron supplementation, excess ethanol ingestion, porphyria cutanea tarda, or hemolytic anemia) [1, 2, 10, 11]. Because serum iron variables in patients with viral hepatitis can mimic those in patients with hemochromatosis and because some patients have both disorders, persons with hemochromatosis must often be evaluated for hepatitis [12-14]. Medical Evaluation before Treatment From each patient, physicians should collect information that includes a review of current and past symptoms and health problems, especially those related to liver, joint, and heart disease; diabetes mellitus and other endocrinopathic conditions; sexual function; and skin pigmentation [1, 2]. A dietary history should focus on general dietary habits and food choices, use of dietary supplements, and ingestion of ethanol. Any history of blood donation, receipt of blood transfusion, and illness associated with blood loss should be documented. The details of menstruation, childbirth, lactation, menopause, and hysterectomy are important (women taking oral contraceptives may have decreased menstrual blood loss or may absorb less dietary iron). The history should include inquiries about family members, especially first-degree relatives. The physical examination must include assessment of the liver, joints, heart, endocrine status, and skin coloration. Certain sequelae of iron overload may require additional specific evaluations to assess management needs (Table 1). Therapeutic Phlebotomy Described in 1952, therapeutic phlebotomy was the first successful treatment for iron overload due to hemochromatosis [15] and is still the preferred treatment for this condition today [1, 2]. The removal of 1 unit of blood (450 to 500 mL) results in the loss of 200 to 250 mg of iron. Although iron chelation and erythrocytapheresis have also been used [16, 17], therapeutic phlebotomy is safer, more efficient, and more economical [1, 2]. Selection of Patients for Treatment Most persons with hemochromatosis benefit from therapeutic phlebotomy (Table 2). Rarely, children and adolescents have severe iron overload (often associated with cardiac and anterior pituitary failure) and need aggressive therapeutic phlebotomy for removal of 1.5 to 2.0 units weekly, if possible [18-20]. Withholding therapeutic phlebotomy from older patients on the basis of age alone is not justifiable. In asymptomatic persons with iron overload (Table 2), therapy must not be delayed until symptoms develop. However, some patients are not candidates for treatment because they are intolerant toward phlebotomy or have limited life expectancy. Patients with severe, refractory anemia require iron chelation therapy [21]. Table 2. Criteria for initiating Therapeutic Phlebotomy in Homozygotes or Heterozygotes for Hemochromatosis Gene or Genes and Other Persons with a Hemochromatosis Phenotype, Regardless of Genotype* Approximately 8% of white persons of western European descent inherit one detectable hemochromatosis gene and thus are heterozygotes [22]. Of the 1% to 3% of heterozygotes who develop iron overload [23], many have a coincidental disorder that increases iron absorption or alters iron metabolism [1, 2, 14]; others may have an additional hemochromatosis mutation or mutations undetectable by current testing methods [24]. Many persons with porphyria cutanea tarda have skin lesions that are alleviated with therapeutic phlebotomy, and many are heterozygous for HFE mutations [2, 25-27]. No study has shown the benefits of therapeutic phlebotomy in other persons with iron overload who are heterozygotes or compound heterozygotes for the hemochromatosis gene or genes. However, we recommend that all persons with iron overload who have a clinical phenotype consistent with hemochromatosis, regardless of genotype, receive therapeutic phlebotomy and management similar to that recommended for homozygotes for classic hemochromatosis (Table 2). Performance of Therapeutic Phlebotomy Therapeutic phlebotomy should be done by experienced persons and should be supervised by a physician. It is usually performed in a physicians office but can be done in a medical laboratory, a blood bank, or a patients home. However, comprehensive management of hemochromatosis is usually accomplished best in a physicians office. For many patients, compliance with treatment is proportional to the skill of the phlebotomist and the confidence of the patient in the treatment staff and environment. Adequate hydration and avoidance of vigorous physical activity for 24 hours after treatment minimize the effects of hypovolemia caused by therapeutic phlebotomy. Persons with a hemoglobin concentration less than 110 g/L or a hematocrit less than 0.33 before treatment are more likely to have symptoms of hypovolemia and anemia, and phlebotomy is less efficient in removing iron in these patients. However, many patients with chronic hemolytic anemia and iron overload tolerate phlebotomy well. The hemoglobin concentration or hematocrit and volume (or weight) of blood removed with each phlebotomy session should be documented. Frequency and Duration of Therapeutic Phlebotomy Depletion of iron stores typically involves the removal of 1 unit of blood weekly until mild hypoferritinemia occurs [1, 2]. Some men and persons with large body mass can sustain removal of 1.5 to 2.0 units of blood weekly. Some women; persons with small body mass; elderly persons; and patients with anemia, cardiac problems, or pulmonary problems can sustain removal of only 0.5 units of blood weekly. After a few weeks of therapeutic phlebotomy, erythroid hyperplasia permits more blood to be removed more often in many patients. Although recombinant human erythropoietin therapy also enhances erythrocyte production, this therapy should be reserved for patients who also have renal dysfunction or anemia of chronic disease [28]. Life expectancy may be substantially decreased in patients in whom iron depletion by phlebotomy cannot be completed within 1 year [29]. Serum ferritin and hepatic iron levels permit a relative estimation of the amount of therapeutic phlebotomy required for iron depletion [2]. On average, men require twice as many units of therapeutic phlebotomy as women do [24, 30, 31]. Older persons typically have more severe iron overload, as do persons who are homozygous for HFE mutation C282Y [2, 24, 32]. Hormonal factors, diet, abnormalities that alter iron absorption, and blood loss also influence the severity of iron overload [33]. Persons who have been regular blood donors often have less severe iron overload than do nondonors [1, 34]. The serum ferritin level is the most reliable, readily available, and inexpensive way to monitor therapeutic phlebotomy; the serum iron level and the transferrin saturation are less suitable [1, 2]. In general, patients who have higher serum ferritin levels have more severe iron overload and need more phlebotomy. Among patients who have serum ferritin levels greater than 1000 g/L before treatment, it is sufficient to quantify the serum ferritin level every 4 to 8 weeks during the initial months of treatment. The serum ferritin level should be measured more often in patients who have received many phlebotomy treatments and in those who have mild or moderate iron overload at diagnosis. In all patients, serum ferritin levels should be quantified a

Disease-Related Conditions in Relatives of Patients with Hemochromatosis

BACKGROUND Hemochromatosis occurs in approximately 5 white people per 1000 and is usually due to homozygosity for mutations in the HLA-linked HFE gene. Although screening has been proposed, the proportion of homozygotes with conditions related to hemochromatosis is uncertain. METHODS We studied the prevalence of disease-related conditions among relatives of probands with hemochromatosis. We identified probands who presented to a clinic with signs or symptoms of hemochromatosis or who had elevated transferrin-saturation values. We identified homozygous relatives, mainly siblings, on the basis of HLA identity with the proband and by HFE genotyping. Disease-related conditions were cirrhosis, hepatic fibrosis, elevated amino-transferase values, and hemochromatotic arthropathy. RESULTS We identified 214 homozygous relatives of 291 homozygous probands. Of the 113 men in this group (mean age, 41 years), 96 (85 percent) had iron overload, and 43 (38 percent) had at least one disease-related condition. Of the 52 men over 40 years of age, 27 (52 percent) had at least one disease-related condition. Of the 101 female homozygous relatives (mean age, 44 years), 69 (68 percent) had iron overload, and 10 (10 percent) had at least one disease-related condition. Of the 43 women over 50 years of age, 7 (16 percent) had at least one disease-related condition. If the proband had a disease-related condition, relatives who were men were more likely to have morbidity than if the proband had no disease-related condition. CONCLUSIONS A substantial number of homozygous relatives of patients with hemochromatosis--more commonly men than women--have conditions related to hemochromatosis that have yet to be detected clinically.

A survey of 2,851 patients with hemochromatosis:: Symptoms and response to treatment

PURPOSE Hemochromatosis is a genetic disorder of iron absorption that affects 5 per 1,000 persons and is associated with reduced health and quality of life. We sought to determine the type and frequency of symptoms that patients experienced before the diagnosis and the treatments that they received. METHODS We mailed a questionnaire to 3,562 patients with hemochromatosis who were located using patient advocacy groups, physicians, blood centers, newsletters, and the Internet. RESULTS Of the 2,851 respondents, 99% were white and 62% were men. Circumstances that led to diagnosis of hemochromatosis included symptoms (35%), an abnormal laboratory test (45%), and diagnosis of a family member with hemochromatosis (20%). The mean (+/- SD) age of symptom onset was 41 +/- 14 years. Symptoms had been present for an average of 10 +/- 10 years before the diagnosis was made. Among the 58% of patients with symptoms, 65% had physician-diagnosed arthritis and 52% had liver disease. The most common and troublesome symptoms were extreme fatigue (46%), arthralgia (44%), and loss of libido (26%). Physician instructions to patients included treatment with phlebotomy (90%), testing family members (75%), and avoiding iron supplements (65%). CONCLUSIONS The diagnosis of hemochromatosis in most patients was delayed. Physician education is needed to increase the detection of patients with the disease and to improve its management.

Homozygosity for Hemochromatosis: Clinical Manifestations

We identified 35 homozygotes for hemochromatosis through pedigree studies. Thirteen were asymptomatic. Arthropathy was present in 20, hepatomegaly in 19, transaminasemia in 16, skin pigmentation in 15, splenomegaly in 14, cirrhosis in 14, hypogonadism in six, and diabetes in two. No homozygote was in congestive failure. Only one had the triad of hepatomegaly, hyperpigmentation, and diabetes. Serum iron was increased in 30 of 35, transferrin saturation was increased in all 35, serum ferritin in 23 of 32, urinary iron excretion after deferoxamine in 28 of 33, hepatic parenchymal cell stainable iron in 32 of 33, and hepatic iron in 27 of 27. Iron loading was 2.7 times greater in men than in women. No female had hepatic cirrhosis. Diagnosis of asymptomatic hemochromatosis is important because organ damage may be prevented by early therapy. Clinical diagnosis of early hemochromatosis is difficult. Persons with unexplained elevation of transferrin saturation should be studied for hemochromatosis.

Hereditary hemochromatosis. Diagnosis in siblings and children.

We studied five patients with clinically manifest hemochromatosis and 19 of their siblings and children to define better the diagnostic criteria for stages of the disease. The earliest detectable abnormalities were an increase in hepatic-parenchymal-cell stainable iron, hepatic iron concentration, transferrin saturation and serum iron concentration. In contrast, urinary iron excretion after deferoxamine and serum ferritin concentration were usually normal in early iron loading. In either latent or clinically manifest disease, hepatic-parenchymal-cell stainable iron was Grade 3 or 4; hepatic iron concentration was greater than 250 microng per 100 mg; serum iron was greater than 170 microng per 100 ml; transferrin saturation was greater than 70 per cent; urinary iron excretion exceeded 2.2 mg per 24 hours; and serum ferritin usually exceeded 1000 ng per ml. Estimation of liver iron is the most sensitive method for detecting early disease. Urinary iron excretion and serum ferritin estimate the total body burden of iron in latent and clinically manifest disease.

Iron overload in African Americans

PURPOSE Iron overload unexplained by dietary or medicinal iron excess, transfusion, or sideroblastic anemia has been described infrequently in Americans of African descent. The purpose of this study was to characterize iron overload attributable to excessive iron absorption in African Americans. PATIENTS AND METHODS In a community hematology and medical oncology practice during the interval 1990 to 1993, we identified and evaluated a series of cases comprised of 6 men and 1 woman, with a mean age of 55 +/- 14 (SD) years (range 33 to 69). Data on clinical features, serum iron parameters, liver and body iron stores, evaluations of anemia, human leukocyte antigen (HLA) typing, and family studies were analyzed. RESULTS Among our patients, the serum iron parameters were: iron concentration 26 +/- 13 mumol/L, transferrin saturation 59 +/- 21%, and ferritin concentration 1,588 +/- 1,053 micrograms/L. Clinical abnormalities observed included weakness and fatigue, decreased libido and impotence, hepatopathy, arthropathy, diabetes mellitus, hypogonadotrophic hypogonadism, and hyperpigmentation. Hepatic parenchymal cell iron deposits were increased in each of the 6 patients studied, and Kupffer cell iron deposits were prominent in 4. The occurrence of iron overload was verified by liver iron quantification and therapeutic phlebotomy. Four subjects had alpha-thalassemia minor; 2 others had hemoglobin S and C traits. No proband had HLA-A3 positivity. Four probands had other family members with iron overload. CONCLUSIONS In comparison with Caucasians with hemochromatosis, our patients have slightly lower mean values of serum iron concentration and transferrin saturation, more Kupffer cell iron deposits, a higher incidence of thalassemia and hemoglobinopathy, and infrequent positivity for HLA-A3. Iron overload in African Americans appears to be more similar to that in certain sub-Saharan African natives than to hemochromatosis.

Haplotype Analysis of Hemochromatosis: Evaluation of Different Linkage-Disequilibrium Approaches and Evolution of Disease Chromosomes

We applied several types of linkage-disequilibrium calculations to analyze the hereditary hemochromatosis (hh) locus. Twenty-four polymorphic markers in the major histocompatibility complex (MHC) class I region were used to haplotype hh and normal chromosomes. A total of 169 hh and 161 normal chromosomes were analyzed. Disequilibrium values were found to be high over an unusually large region beginning 150 kb centromeric of HLA-A and extending nearly 5 Mb telomeric of it. Recombination in this region was approximately 28% of the expected value. This low level of recombination contributes to the unusually broad region of linkage disequilibrium found with hh. The strongest disequilibrium was found at locus HLA-H (delta = .84) and at locus D6S2239 (delta = .85), a marker approximately 10 kb telomeric to HLA-H. All disequilibrium methods employed in this study found peak disequilibrium at HLA-H or D6S2239. The cys282tyr mutation in HLA-H, a candidate gene for hh, was found in 85% of disease chromosomes. A haplotype phylogeny for hh chromosomes was constructed and suggests that the mutation associated with the most common haplotype occurred relatively recently. The age of the hh mutation was estimated to be approximately 60-70 generations. Disequilibrium was maintained over a greater distance for hh-carrying chromosomes, consistent with a recent mutation for hh. Our data provide a reasonable explanation for previous difficulties in localizing the hh locus and provide an evolutionary history for disease chromosomes.