Hemochromatosis--neonatal and young subjects

Primary biliary cirrhosis-specific antimitochondrial antibodies in neonatal haemochromatosis

Background and Aim. Neonatal hemochromatosis (NH) is characterised by severe liver injury and extrahepatic siderosis sparing the reticuloendothelial system. Its aetiology is obscure, although it has been proposed as an alloimmune disease, resulting from immunological reaction to self-antigens (alloantigens) which the body recognizes as foreign. We studied an infant with NH and his mother whose sera contained antimitochondrial antibody (AMA), the hallmark of primary biliary cirrhosis (PBC). Material and Methods. To investigate the origin of AMA in the infant, we studied isotype distributions in serum from the mother and infant. Serum samples were obtained at diagnosis of NH, after liver transplantation (LT; age 1 month), and over the ensuing 17 months. Results. At NH diagnosis, infant and maternal serum contained AMA of the IgG isotype, predominantly of the G3 and G1 subclasses. AMA strongly reacted against the pyruvate dehydrogenase complex E2 subunit (PDC-E2), the major PBC-specific AMA autoantigen. Anti-PDC-E2 responses in both infant and mother declined over time, being present 2 months after LT (mother and child) and absent 10 months later (mother) and 17 months later (child). Conclusion. The association of maternally transferred IgG1 and IgG3 subclass AMA with the appearance of liver damage in an infant with NH may suggest a causal link between antibody and liver damage.

Therapeutic management of neonatal hemochromatosis: Report of four cases and literature review

Neonatal hemochromatosis (NH) is a rare disease of iron metabolism that starts at intrauterine period causing liver failure and extrahepatic siderozis. The etiology of NH has not been understood exactly, yet it is accepted that a maternofetal alloimmune disorder that leads to liver failure in fetus causes the illness. The prognosis of NH is generally bad and death is inevitable if left untreated. The efficiency of chelation–antioxidant coctail used in medical treatment is between 10% and 20% and these patients frequently need liver transplantation. In our study, we presented four newborn cases diagnosed as NH and treated medically. Of the four patients, one died of pulmonary hemorrhage and another died of multiorgan failure in the first week of hospitalization. The other two patients' clinical status and laboratory parameters recovered with medical treatment. However, since liver transplantation was not carried out, one of these patients died at the age of two and a half months and the other at eighth month due to sepsis. In this study, we would like to emphasize the importance of early liver transplantation in patients recovered with medical treatment.

Lack of the bone morphogenetic protein BMP6 induces massive iron overload

Expression of hepcidin, a key regulator of intestinal iron absorption, can be induced in vitro by several bone morphogenetic proteins (BMPs), including BMP2, BMP4 and BMP9 (refs. 1,2). However, in contrast to BMP6, expression of other BMPs is not regulated at the mRNA level by iron in vivo, and their relevance to iron homeostasis is unclear. We show here that targeted disruption of Bmp6 in mice causes a rapid and massive accumulation of iron in the liver, the acinar cells of the exocrine pancreas, the heart and the renal convoluted tubules. Despite their severe iron overload, the livers of Bmp6-deficient mice have low levels of phosphorylated Smad1, Smad5 and Smad8, and these Smads are not significantly translocated to the nucleus. In addition, hepcidin synthesis is markedly reduced. This indicates that Bmp6 is critical for iron homeostasis and that it is functionally nonredundant with other members of the Bmp subfamily. Notably, Bmp6-deficient mice retain their capacity to induce hepcidin in response to inflammation. The iron burden in Bmp6 mutant mice is significantly greater than that in mice deficient in the gene associated with classical hemochromatosis (Hfe), suggesting that mutations in BMP6 might cause iron overload in humans with severe juvenile hemochromatosis for which the genetic basis has not yet been characterized.

[Endocrine consequences of hemochromatosis]

The two most frequent endocrine complications of hemochromatosis are diabetes mellitus and hypogonadotrophic hypogonadism. Other endocrine disorders related to this disease are very rare and are described especially in the most severe and earliest posttransfusion iron overloads. Endocrine complications are evidence of advanced hemochromatosis, often already associated with cirrhosis. Given the low frequency of HFE mutations in type 2 diabetes, routine genetic testing in this population does not seem reasonable. Testing for iron overload is recommended in subjects with atypical type 2 diabetes (for example, patients who are not overweight) and in cases of hypogonadism, characteristic pigmentation, or cirrhosis. Phlebotomy plays an important role in the management of endocrine complications of hemochromatosis, especially when diagnosis is early. In all cases of hypogonadotrophic hypogonadism, primary hemochromatosis must be considered.

Iron Overload (with Attention to Genetic Testing and Diagnosis/Management of HFE Wild Type Patients)

The discovery of the HFE, HJV, HAMP, TfR2, and SLC40A1 genes and preliminary understanding of their roles in iron homeostasis have contributed tremendously to our understanding of the pathogenesis of genetic hemochromatosis. Although several new models of iron metabolism have been proposed, some key "sensor" steps of iron absorption in the enterocytes and of iron storage in hepatocytes and other cells remain unclear. A diagnosis of non-HFE genetic hemochromatosis should be considered in patients with unexplained iron overload who do not have the common mutations in the HFE genes. Phenotypic evaluation such as liver biopsy and measurement of hepatic iron concentration remain important in non-HFE hemochromatosis because mutations in other genes are rare and there are no other available noninvasive tests to confirm the diagnosis. Phlebotomy remains the mainstay of therapy also for non-HFE hemochromatosis. However, phlebotomy may not be well tolerated in certain forms of non-HFE hemochromatosis such as "ferroportin disease."

Molecular and clinical aspects of iron homeostasis: From anemia to hemochromatosis

The discovery in recent years of a plethora of new genes whose products are implicated in iron homeostasis has led to rapid expansion of our knowledge in the field of iron metabolism and its underlying complex regulation in both health and disease. Abnormalities of iron metabolism are among the most common disorders encountered in practical medicine and may have significant negative impact on physical condition and life expectancy. Basic insights into the principles of iron homeostasis and the pathophysiological and clinical consequences of iron overload, iron deficiency and misdistribution are thus of crucial importance in modern medicine. This review summarizes our current understanding of human iron metabolism and focuses on the clinically relevant features of hereditary and secondary hemochromatosis, iron deficiency anemia, anemia of chronic disease and anemia of critical illness. The interconnections between iron metabolism and immunity are also addressed, in as much as they may affect the risk and course of infections and malignancies.

Hereditary Hemochromatosis

In recent years, the number of proteins implicated in iron homeostasis has increased dramatically, and genetic causes have apparently been identified for the major disorders associated with tissue iron overload. These dramatic steps forward have transformed the way we look at iron-related disorders, particularly hemochromatosis. This review presents a concept of this disease that is based on this new knowledge and stems from the idea that, beyond their genetic diversities, all known hemochromatoses originate from the same metabolic error, the genetic disruption of human tendency for circulatory iron constancy. Hepcidin, the iron hormone, seems to hold a central pathogenic place in hemochromatosis, similar to insulin in diabetes: Genetically determined lack of hepcidin synthesis or activity may cause the disease.

Disparate clinical presentation of neonatal hemochromatosis in twins

Neonatal hemochromatosis (NH) is a rare disease of gestation that results in fetal liver injury and extrahepatic siderosis. The etiology of NH is not fully understood. However, the rate of recurrence of NH in the pregnancy after an affected one is approximately 80%. A spectrum of liver disease has been recognized, spanning from liver failure in the fetus or neonate to infants that survive with medical therapy. Here we report on 2 sets of fraternal twins, each set with a gross disparity in the severity of presentation: 1 infant with liver failure and the other nearly unaffected. These findings suggest a need to look carefully for subclinical disease in the siblings of patients with NH by using sensitive tests such as those for ferritin and alpha-fetoprotein. They also suggest that affected infants may be missed when using routine clinical testing, which would lead to the apparent rate of recurrence, understating the actual recurrence rate.

Neonatal hemochromatosis: fetal liver disease leading to liver failure in the fetus and newborn

Acute liver failure in the newborn is relatively rare but often fatal. The broadest definition of acute liver failure is failure of the vital functions of the liver occurring within weeks or a few months of the onset of clinical liver disease. Therefore, by definition, any liver failure in the newborn can be construed to be acute liver failure. A second component of the general definition of acute liver failure is the lack of known preexisting liver disease. In the case of neonatal acute liver failure, preexisting disease would by definition be liver disease that affects the fetus. Almost nothing is known about fetal onset liver failure, and there is no literature addressing the subject. This review will address fetal liver disease that leads to liver failure in the fetus or newborn.

Iron homeostasis and inherited iron overload disorders: an overview

Iron is an ubiquitous metal of vital importance to the normal physiologic processes of many organisms. Recent discoveries of mutations in genes that lead to inherited iron overload diseases have advanced the understanding of iron homeostasis in humans. This article provides an overview of the human iron cycle, regulation of iron homeostasis, how perturbations in this homeostasis lead to iron overload disease in adults and children, and strategies for diagnosis of inherited iron overload.

High-dose immunoglobulin during pregnancy for recurrent neonatal haemochromatosis

BACKGROUND

Neonatal haemochromatosis is a rare disease of gestation that results in severe fetal liver injury. We hypothesised an alloimmune aetiology for the disorder on the basis of its high recurrence rate in sibships. In this study, we assessed the effectiveness in preventing or changing the severity of recurrent neonatal haemochromatosis of administering during pregnancy high-dose intravenous immunoglobulin (IVIG) derived from pooled serum of multiple donors.

METHODS

Women whose most recent pregnancy ended in documented neonatal haemochromatosis were treated with IVIG, 1 g/kg bodyweight, weekly from the 18th week until the end of gestation in their subsequent pregnancy. The outcomes of treated pregnancies were compared with those of randomly selected previous affected pregnancies for each woman, which were used as historical controls.

FINDINGS

15 women were treated through 16 pregnancies. All pregnancies progressed uneventfully and resulted in live babies with normal physical examinations and birthweights that were appropriate for gestational age. 12 babies had evidence of liver involvement with neonatal haemochromatosis: 11 had higher than normal concentrations of serum alpha-fetoprotein and ferritin or serum alpha-fetoprotein alone, including four with coagulopathy (international normalised ratio >1.5), and one had coagulopathy alone. All babies survived with medical or no treatment and were healthy at follow-up within the past 6 months. In analysis on a per-mother basis comparing outcomes of treated gestations with those of randomly selected previous affected gestations, gestational IVIG therapy was associated with better infant survival (15 good outcomes vs two in previous pregnancies; p=0.0009).

INTERPRETATION

Treatment with high-dose IVIG during gestation appears to have modified recurrent neonatal haemochromatosis so that it was not lethal to the fetus or neonate. These results further support an alloimmune mechanism for recurrent neonatal haemochromatosis.

Influence of gestational age and fetal iron status on IRP activity and iron transporter protein expression in third-trimester human placenta

Placental iron transport during the last trimester of pregnancy determines the iron endowment of the neonate. Iron transport is a function of the major iron transport proteins: transferrin receptor-1 (TfR-1) and ferroportin-1 (FPN-1). The mRNAs for TfR-1 and, potentially, FPN-1 are posttranscriptionally regulated by iron regulatory protein (IRP)-1 and IRP-2. We assessed the effect of gestational age and fetal iron status on IRP-1- and IRP-2-binding activity and on the localization and protein expression of TfR-1 and FPN-1 protein at 24-40 wk of gestation in 21 placentas obtained from iron-sufficient nonanemic mothers. Gestational age had no effect on cord serum ferritin concentration, IRP-2 RNA-binding activity, transporter protein location, and TfR-1 or FPN-1 protein expression. IRP-1 activity remained constant until full term, when it decreased (P = 0.01). Placental ferritin (r = 0.76, P < 0.001) and FPN-1 (r = 0.44, P < 0.05) expression increased with gestational age. Fetal iron status, as indexed by cord serum ferritin concentration, was inversely related to placental IRP-1 (r = -0.66, P < 0.001) and IRP-2 (r = -0.42, P = 0.05) activities. Placental ferritin protein expression correlated better with IRP-1 (r = -0.45, P = 0.04) than with IRP-2 (r = -0.35, P = 0.10) activity. Placental TfR-1 and FPN-1 protein expression was independent of fetal or placental iron status and IRP activities. Iron status had no effect on transport protein localization. We conclude that, toward the end of the third trimester of iron-sufficient human pregnancy, the placenta accumulates ferritin and potentially increases placental-fetal iron delivery through increased FPN-1 expression. IRP-1 may have a more dominant role than IRP-2 activity in regulating ferritin expression.

Hepcidin, a key regulator of iron metabolism and mediator of anemia of inflammation

Human hepcidin, a 25-amino acid peptide made by hepatocytes, may be a new mediator of innate immunity and the long-sought iron-regulatory hormone. The synthesis of hepcidin is greatly stimulated by inflammation or by iron overload. Evidence from transgenic mouse models indicates that hepcidin is the predominant negative regulator of iron absorption in the small intestine, iron transport across the placenta, and iron release from macrophages. The key role of hepcidin is confirmed by the presence of nonsense mutations in the hepcidin gene, homozygous in the affected members, in 2 families with severe juvenile hemochromatosis. Recent evidence shows that deficient hepcidin response to iron loading may contribute to iron overload even in the much milder common form of hemochromatosis, from mutations in the HFE gene. In anemia of inflammation, hepcidin production is increased up to 100-fold and this may account for the defining feature of this condition, sequestration of iron in macrophages. The discovery of hepcidin and its role in iron metabolism could lead to new therapies for hemochromatosis and anemia of inflammation.