Evidence for heterogeneity in hereditary hemochromatosis: Evaluation of 174 persons in nine families

Hereditary hemochromatosis is an autosomal recessive disease in which the gene is linked to the HLA system. Investigation of nine unrelated probands and their family members has revealed distinct groups based on biochemical and clinical manifestations of the disease. Four different types of disease expression were identified: Group I—classic hereditary hemochromatosis with elevated transferrin saturation, serum ferritin levels, and liver iron content; Group II—severe iron overload, accelerated disease manifesting at an early age; Group III—elevated total body iron stores, normal transferrin saturation and serum ferritin levels; Group IV—markedly elevated findings on serum biochemical tests, e.g., transferrin saturation, serum ferritin levels, with minimal elevation in total body iron stores. This evidence for several clearly distinguishable modes of expression in different families suggests that more than one genetic lesion in iron metabolism may be responsible for iron overload in hereditary hemochromatosis. This genetic heterogeneity may be helpful in delineating the fundamental abnormalities in iron metabolism in this group of disorders.     

Time-course analysis of serum hepcidin,iron and cytokines in a C282Y homozygous patient with Schnitzler’s syndrome treated with IL-1 receptor antagonist

It is currently unknown if the increase of the hepatic iron regulatory hormone hepcidin during inflammation in man depends on an intact HFE-protein. Here we describe the temporal relationship of serum hepcidin, serum iron and cytokines in a patient with HFE-related (C282Y homozygous) hereditary hemochromatosis who was treated for an auto-inflammatory condition, i.e. variant Schnitzler’s syndrome, with the potent anti-inflammatory cytokine inter-leukin-1 receptor antagonist (IL-1ra, anakinra). The patient had bouts of fever with peaking serum IL-6 concentrations followed by peaking serum hepcidin levels, while serum iron was low. Upon treatment, these peaks disappeared and hepcidin levels became non-detectable, consistent with HFE deficiency. In conclusion, this in vivo human model: i) supports the importance of an HFE-independent IL-6-hepcidin axis in the development of hypoferremia and anemia of inflammation; and ii) suggests that chronic inflammation protects patients with HFE-related hereditary hemochromatosis from iron accumulation.     

Hypouricemia and hyperuricosuria as expressions of renal tubular damage in primary biliary cirrhosis

Renal tubular damage, in particular, renal tubular acidosis is associated with primary biliary cirrhosis (PBC), but hypouricemia has not been described. We studied four patients with PBC whose serum uric acid levels were 1.4 to 1.8 mg per dl, and compared their renal and liver functions with those of 11 patients with PBC whose serum uric acid levels were normal. In the patients with PBC and hypouricemia, uric acid clearance (Cua) and the ratio of Cua and creatinine clearance (Cua/Ccr) were high enough to cause hypouricemia. Elevated Cua/Ccr was suppressed by administration of pyrazinamide, a blocker of tubular secretion of uric acid, but was not affected by probenecid; the effects of drugs on Cua/Ccr were similar to those reported in Wilson's disease. Elevation in Cua/Ccr was associated with increased serum bilirubin and urinary copper excretion. These observations indicate that hypouricemia and hyperuricosuria, which may be caused by defective postsecretory reabsorption of uric acid, are additional indicators of renal tubular damage in PBC.     

Increased duodenal DMT-1 expression and unchanged HFE mRNA levels in HFE-associated hereditary hemochromatosis and iron deficiency

HFE-associated hereditary hemochromatosis is characterized by imbalances of iron homeostasis and alterations in intestinal iron absorption. The identification of the HFE gene and the apical iron transporter divalent metal transporter-1, DMT-1, provide a direct method to address the mechanisms of iron overload in this disease. The aim of this study was to evaluate the regulation of duodenal HFE and DMT-1 gene expression in HFE-associated hereditary hemochromatosis. Small bowel biopsies and serum iron indices were obtained from a total of 33 patients. The study population comprised 13 patients with hereditary hemochromatosis (C282Y homozygous), 10 patients with iron deficiency anemia, and 10 apparently healthy controls, all of whom were genotyped for the two common mutations in the HFE gene (C282Y and H63D). Total RNA was isolated from tissue and amplified via RT-PCR for HFE, DMT-1, and the internal control GAPDH. DMT-1 protein expression was additionally assessed by immunohistochemistry. Levels of HFE mRNA did not differ significantly between patient groups (P = 0.09), specifically between C282Y homozygotes and iron deficiency anemic patients, when compared to controls (P = 0.09, P = 0.9, respectively). In contrast, DMT-1 mRNA levels were at least twofold greater in patients with hereditary hemochromatosis and iron deficiency anemia when compared to controls (P = 0.02, P = 0.01, respectively). Heightened DMT-1 protein expression correlated with mRNA levels in all patients. Loss of HFE function in hereditary hemochromatosis is not derived from inhibition of its gene expression. DMT-1 expression in C282Y homozygote subjects is consistent with the hypothesis of a "paradoxical" duodenal iron deficiency in hereditary hemochromatosis. The observed twofold upregulation of the DMT-1 is consistent with the slow but steady increase in body iron stores observed in those presenting with clinical features of hereditary hemochromatosis.     

Significance of "minor" genetic mutations in hereditary hemochromatosis: 2 case reports

We describe a case of homozygosity due to the substitution of aspartic acid with histidine at position 63 of the protein encoded by the gene (known as HFE) associated with hereditary hemochromatosis. Liver biopsy did not disclose stainable iron accumulation; serum ferritin was elevated (639 ng/mL), while the transferrin saturation index was within the normal range (38.1%). As the patient was affected by chronic hepatitis C virus, the high serum ferritin could be attributed to this disease, a frequent occurrence. We also describe a case of heterozygosity for both the substitution of tyrosine with cysteine at position 282 and the substitution of histidine to aspartic acid at position 63 (so-called "compound heterozygosity"). The patient had the typical biochemical abnormalities of iron overload: transferrin saturation index of 53.1% and elevated serum ferritin (658 ng/mL). The removal of > 5 g of iron by phlebotomies did not precipitate iron deficiency. Although the patient refused to undergo liver biopsy, clinical evidence alone enabled a diagnosis of hemochromatosis. These two cases concord with the present scientific orientation, i.e.: 1) homozygosity for the major mutation is associated with the phenotypical (clinical) picture of hemochromatosis, but compound heterozygosity also determines significant iron metabolism abnormalities; 2) homozygosity for the minor mutation does not appear to determine important phenotypical abnormalities.     

Iron overload complicating sideroblastic anemia--is the gene for hemochromatosis responsible?

Idiopathic hemochromatosis is a hereditary disease that is associated with human leucocytic antigens A3, B7, and B14. A genetic association between human leucocytic antigen-linked hemochromatosis and idiopathic refractory sideroblastic anemia has been suggested that may predispose some patients with idiopathic refractory sideroblastic anemia to develop gross iron overload. Study of the family of a patient with idiopathic refractory sideroblastic anemia and hemochromatosis revealed that 2 of 5 first-degree relatives had significant elevations of serum ferritin, and a shared human leucocytic antigen haplotype, supporting the concept that patients with idiopathic refractory sideroblastic anemia and significant iron overload have at least one allele for hemochromatosis.     

Congenital spherocytosis with hereditary hemochromatosis without pathogenic mutations in the HFE gene

We report a case of an 80-year-old woman with congenital spherocytosis who presented with massive iron overload. Iatrogenic iron overload could be ruled out. Familial history was suggestive of hereditary hemochromatosis; however, molecular genetic testing for the most common HFE mutations remained negative. The patient was treated successfully with phlebotomies. The hypothesis that this patient suffered from hereditary hemochromatosis is discussed on the basis of a brief review of the literature.     

Familial hyper- and hypouricemias in random and hyperlipidemic recall cohorts: the Princeton School District Family Study

Using the Princeton School Family Study, our specific aim was to estimate the prevalence of familial hyper- and hypouricemia, to estimate the proportion of probands' first-degree relatives who were similarly affected, and to evaluate the contribution of diseases, drugs, and alcohol intake (if any) to uric acid levels. We studied 379 probands and a total of 1928 subjects, 125 and 52 black probands from a randomly recalled group, 147 white and 55 black probands from a hyperlipidemic recall (top decile cholesterol and/or triglyceride) group. Familial hyper- and hypouricemias were arbitrarily identified in those kindreds having at least two first-degree relatives in the same decile as the proband, top or bottom respectively, for serum uric acid. No probands had symptomatic gout. Diseases, drugs, and alcohol intake were not consistently associated with aggregations of high and/or low uric acid levels in families, and had little relationship to uric acid levels in individuals. Of the 177 randomly recalled probands, and of the 55 black probands in hyperlipidemic recall familial hyperuricemia, with concurrent primary hyperlipoproteinemia and hypertension. Familial hypouricemia was present in 1 of 125 white and in 1 of 52 randomly recalled black kindreds, and in 3 of 147 white and 3 of 55 hyperlipidemic recall black kindreds. While familial clustering of hyperuricemia was limited, clustering of hypouricemia was much more marked. Seventy-four and 84% respectively of first-degree relatives of hypouricemic white and black probands had uric acid less than the 50th percentile. In randomly recalled probands and their first-degree relatives there were significant inverse partial correlations between uric acid and high density lipoprotein cholesterol. Inverse associations of uric acid with high density lipoprotein cholesterol and the concurrence of hyperlipoproteinemia and hypertension in hyperuricemic families points to the importance of lipoprotein and blood pressure screening in families with asymptomatic hyperuricemia. The potential ramifications of within-family clustering of hypouricemia need to be further assessed in populations, particularly in regards to uric acid nephrolithiasis.     

Iron overload in hereditary spherocytosis: Association with hla-linked hemochromatosis

Heavy iron loading is a rare clinical finding in patients with hereditary spherocytosis. A pedigree was studied in which the proband, a 38-year-old man, had both hereditary spherocytosis and overt hemochromatosis. He had never received blood transfusions. The 8-year-old son of the proband also had hereditary spherocytosis and mildly increased iron stores. The 39-year-old brother of the proband did not have spherocytosis but did have overt hemochromatosis. Since hemochromatosis is transmitted as an HLA-linked autosomal recessive disorder, HLA haplotypes serve as markers of hemochromatosis alleles. In this pedigree only individuals with two hemochromatosis alleles (homozygosity) had heavy iron loads, whether hereditary spherocytosis was present or not. The presence of hereditary spherocytosis may have contributed to the magnitude of the iron loading but was not a major factor. Our findings suggest that nontransfusional hemochromatosis found in association with hereditary spherocytosis is due primarily to homozygosity for hemochromatosis.     

Arthropathy in hereditary hemochromatosis

Arthropathy is one of the leading clinical manifestations of hereditary hemochromatosis (HH). Although cirrhosis of the liver is crucial for mortality in patients with HH, arthropathy has the greatest impact on the quality of life.Several mutations in the HFE and other genes have recently been identified, and the prevalence of some of these mutations has already been investigated in population studies in greater detail. Even though cofactors other than genetic predisposition may play a role in the establishment of the disease, the new understanding of the genetic background of this iron storage disorder may help in identifying patients before the onset of clinical symptoms. Early initiation of iron depletion therapy, not effective in established arthropathy of HH, might prevent the manifestation of arthropathy or reduce its severity.     

Hemochromatosis heterozygotes may have significant iron overload when they also have hereditary spherocytosis

A family is described in which four of six siblings have both hereditary spherocytosis and evidence of abnormal iron metabolism. Three of the four have significant iron overload. HLA typing, which permits the detection of the gene for hemochromatosis, indicates that all family members with hereditary spherocytosis who have abnormal iron metabolism or significant iron overload are heterozygous for the hemochromatosis gene. Family members having hereditary spherocytosis but not the gene for hemochromatosis have normal iron studies as does a family member heterozygous for hemochromatosis but no hereditary spherocytosis. Based on the findings in this kindred, it appears that the combination of chronic hemolysis and the gene for hemochromatosis results in increased iron absorption that may lead to significant iron overload.     

Transferrin sialic acid contents of patients with hereditary hemochromatosis

Recent evidence suggests that asialotransferrin may enhance hepatic uptake of trivalent metal ions through the asialoglycoprotein-receptor pathway. In hereditary hemochromatosis, there is preferential uptake of iron by hepatocytes. We purified transferrin from two patients with this disease. Their transferrins had normal electrophoretic patterns and contained normal amounts of sialic acid. We conclude that the preferential uptake of iron by hepatocytes in hereditary hemochromatosis is not due to the presence of asialotransferrin in their plasma.     

Juvenile hemochromatosis associated with pathogenic mutations of adult hemochromatosis genes

BACKGROUND AND AIMS: Juvenile hemochromatosis is a severe form of hereditary iron overload that has thus far been linked to pathogenic mutations of the gene coding for hemojuvelin (HJV), on chromosome 1, or, more rarely, that coding for hepcidin ( HAMP ), on chromosome 19. A milder adult-onset form is due to pathogenic mutations of HFE or, rarely, serum transferrin receptor 2. METHODS: We studied a pedigree with siblings affected by both juvenile and adult-onset hereditary hemochromatosis. Affected subjects underwent full clinical evaluation, as well as microsatellite and gene sequencing analysis. RESULTS: Two siblings (male and female, aged 24 and 25 years, respectively) were hospitalized for severe endocrinopathy and cardiomyopathy. At age 18 and 17 years, they had presented with impotence and amenorrhea, respectively, and increased serum iron levels. Hypogonadotropic hypogonadism was confirmed in both, and liver biopsy showed marked hepatic iron accumulation and micronodular cirrhosis. Iron levels were normalized after 24 months (female) and 36 months (male) of weekly phlebotomies. Microsatellite analysis showed no linkage with chromosome 1 and 19, and gene sequencing showed no hemojuvelin or hepcidin gene mutations. Instead, combined mutations of HFE (C282Y/H63D compound heterozygosity) and serum transferrin receptor 2 (Q317X homozygosity) were found. A 21-year-old brother with a milder phenotype resembling classic adult-onset hereditary hemochromatosis carried only the Q317X serum transferrin receptor 2 homozygote mutation. CONCLUSIONS: Juvenile hereditary hemochromatosis is not a distinct monogenic disorder invariably due to hemojuvelin or hepcidin mutations: it may be genetically linked to the adult-onset form of hereditary hemochromatosis.     

Hypouricemia and tubular transport of uric acid

Hypouricemia is defined when a serum urate concentration is less than or equal 2.0mg/dl. Differential diagnosis is made by fractional uric acid excretion with the identification of urate transporters and intracellular proteins involved in the tubular transport of uric acid. This review examines current knowledge on uric acid tubular transport and the various clinical situations of hypouricemia.     

A homozygous HFE gene splice site mutation (IVS5+1 G/A) in a hereditary hemochromatosis patient of Vietnamese origin

The vast majority of Caucasian patients presenting with hereditary hemochromatosis demonstrate a single homozygous missense mutation in the HFE gene (C282Y). The underlying genetic defects in hemochromatosis patients of non-Caucasian origin are largely unknown. A 48-year-old man of Vietnamese origin presented with insulin-dependent diabetes mellitus, tertiary adrenocortical insufficiency, and laboratory results highly indicative of hereditary hemochromatosis. Because the patient was negative for the known HFE gene mutations C282Y, H63D, and S65C HFE, the entire coding region and intron/exon boundaries of the HFE gene was investigated. Sequencing studies identified a homozygous G-to-A transition at position +1 of intron 5 (IVS5+1 G/A). This newly described mutation alters the invariant G at position +1 of the 5' splice site causing altered mRNA splicing and exon skipping with exon 4 being spliced to exon 6. Both heterozygously affected children (age 19 and 20 years) had moderately increased ferritin levels with normal serum iron concentration and transferrin saturation. The newly described mutation was not detected in a control group consisting of 220 Caucasian individuals as verified by allele-specific polymerase chain reaction. We describe for the first time a homozygous HFE splice site mutation (IVS5+1 G/A) in a non-Caucasian patient with hereditary hemochromatosis. Although the absence of this novel HFE gene mutation in Caucasian subjects suggests that the mutation is exclusive to this family, mutation screening in populations of different ethnic background is recommended to precisely define its contribution to hereditary hemochromatosis in non-Caucasian patients.     

Haptoglobin phenotype 2-2 overrepresentation in Cys282Tyr hemochromatotic patients

Background/Aims: Patients with genotypic Cys282Tyr homozygous hemochromatosis differ largely in phenotypic presentation. The HFE mutation on itself does not explain the different manifestations of hemochromatosis. We hypothesized that the genetic haptoglobin (Hp) polymorphism, because of its effect on iron metabolism, could be a modifying factor that influences the clinical presentation of hereditary hemochromatosis.Methods: In 167 Cys282Tyr homozygous hemochromatotic patients, the frequencies of Hp types (1-1, 2-1 and 2-2) and alleles (Hp1, Hp2) were compared with those in 918 healthy subjects. Clinical and laboratory indices of iron overload were incorporated in the analysis.Results: The Hp 2-2 type was overrepresented in the patient group (P<0.01). Male patients carrying Hp 2-2 had higher serum iron (P=0.003) and ferritin levels (P=0.03) than those with a Hp 1-1 or 2-1 type. The amount of iron removed with phlebotomy was also higher in Hp 2-2 patients (P=0.03).Conclusions: The Hp 2-2 type is overrepresented among Cys282Tyr homozygous hemochromatotic patients. At diagnosis, iron overload was more pronounced in male patients carrying Hp 2-2. Our data suggest that Hp polymorphism affects iron metabolism in hereditary hemochromatosis.     

Hereditary hemochromatosis in a patient with congenital dyserythropoietic anemia

Herein is described the case of a young woman presenting with iron overload and macrocytosis. The initial diagnosis was hereditary hemochromatosis. Severe anemia developed after a few phlebotomies, and she was also found to have congenital dyserythropoietic anemia that, though not completely typical, resembled type II. Only genetic testing allowed the definition of the coexistence of the 2 diseases, both responsible for the iron overload. This report points out the need to consider congenital dyserythropoietic anemia in patients with hemochromatosis and unexplained macrocytosis and, conversely, to check for the presence of hereditary hemochromatosis in patients with congenital dyserythropoietic anemia and severe iron overload. To the authors' knowledge, this is the first report of homozygosity for the C282Y mutation of the HFE gene in a patient affected by congenital dyserythropoietic anemia.     

Iron overload states

Hereditary hemochromatosis is a common disorder of iron metabolism that increasingly is diagnosed and treated prior to the development of cirrhosis or diabetes. The discovery of a candidate gene for hereditary hemochromatosis undoubtedly will result in improved diagnosis of hereditary hemochromatosis and to a better understanding of certain aspects of iron absorption, hepatic iron uptake and release, and whole body iron metabolism. In turn, this enhanced understanding of iron biology can be applied to the observations seen in patients with other hepatic diseases such as chronic viral hepatitis.     

Hipouricemia renal hereditaria tipo 1 y 2 en tres niños españoles. Revisión de casos pediátricos publicados

Hereditary renal hypouricemia is a rare autosomal recessive genetic disorder that involves an isolated defect in uric acid reabsorption at the renal tubules. Patients present with serum uric acid concentrations of less than 2mg/dl (119 micromol/L) with increased fractional excretion above 10%. Most of the patients are asymptomatic and are detected incidentally. However, complications such us nephrolithiasis, hematuria, acute renal failure exercise-induced or after dehydration for acute gastroenteritis, or posterior reversible encephalopaty syndrome (PRES) may develop.Hereditary renal hypouricemia is confirmed by molecular genetic analysis of the two genes which codify the uric acid transport in the kidney tubules. The renal hypouricemia type 1 (OMIM 220150) is characterized by loss-of-function mutations in the SLC22A12 gene which encodes URAT 1 transporter, and the hypouricemia type 2 (OMIM 612076) is caused by defects in the SLC2A9 gene. Homozygous mutations of SLC2A9 cause the most severe forms of the disease.Most mutations have been identified in Japanese adults, and only a few in children.We describe three asyntomatic pediatric Spanish patients with renal hypouricemia, with genetic confirmation, and we make a revision of all of the pediatric cases with genetic study published in the literature.