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This article is for Medical Professionals

This article is for Medical Professionals

Synonyms: genetic haemochromatosis, HLA-linked haemochromatosis, bronze diabetes

Hereditary haemochromatosis (HHC) is an heterogeneous group of disorders related to deficiency of the iron regulatory hormone hepcidin. HHC is an autosomal recessive genetic disease in which increased intestinal absorption of iron causes accumulation in tissues, especially the liver, which may lead to organ damage. Other organs that may be affected by iron deposits include the pancreas, joints, heart, skin and gonads.

Liver fibrosis, cirrhosis and hepatocellular carcinoma are the most serious complications of iron overload. Early diagnosis and treatment are therefore essential.[1]

Aetiology and epidemiology[2]

Defects of the HFE gene (located on the short arm of chromosome 6) cause the majority of cases of inherited haemochromatosis, which is therefore often referred to as HFE haemochromatosis (HFE-HC). HFE was the only known gene associated with haemochromatosis but it is now known that there are other genetic associations.

A systematic review has shown that about 0.4% of people of northern European descent have the genetic mutation that increases the risk of developing haemochromatosis but the clinical penetrance of the mutation is much lower than the genetic prevalence.[3]

The known mutations of the HFE gene are C282Y and H63D. The C282Y mutation is most common in white populations.[4]The prevalence of C282Y homozygosity in a meta-analysis of 2,802 haemochromatosis patients of European ancestry was 80.6%. HHC is a relatively common genetic disorder in northern European populations and is probably under-diagnosed.[3]

Haemochromatosis is inherited in an autosomal recessive pattern but the clinical picture is more complex because the expression (penetrance) of the gene varies. This means that not everyone who is homozygous for HHC genes will develop clinical disease. The variation in gene expression may be due to other factors affecting iron accumulation.

Other types of inherited haemochromatosis:

There are rarer forms of inherited haemochromatosis, where patients have 'classical' clinical features of haemochromatosis but lack mutations in the HFE gene.

Juvenile haemochromatosis is an inherited condition in which there is clinical onset in the second or third decade. The gene responsible is probably located on chromosome 1.

African iron overload is a syndrome originally ascribed to drinking beer brewed in iron containers; however, a genetic influence has been detected.

Neonatal haemochromatosis is a condition of acute liver damage with iron accumulation. This includes severe iron overload of unknown cause in neonates.

Presentation

Early diagnosis is difficult because HHC is often asymptomatic until the late stages of disease. Symptoms usually start between ages 40-60 in males and after the menopause in females. [5]

Initial symptoms are usually vague and nonspecific - eg, fatigue, weakness, arthropathy affecting various joints, nonspecific abdominal problems, erectile dysfunction and heart problems. [3]

HHC may be diagnosed incidentally - eg, following abnormal serum ferritin or LFTs.

Symptoms of advanced disease include diabetes, bronzing of the skin, hepatomegaly and arthropathy, especially of the second and third metacarpophalangeal joints. [3] Other presenting features of advanced disease include: Impotence, amenorrhoea or hypogonadism. Cirrhosis. Diabetes mellitus. Cardiac disease - arrhythmias or cardiomyopathy. Neurological or psychiatric symptoms - impaired memory, mood swings, irritability, depression.

Other presenting features of advanced disease include:

Screening

Recommendations for genetic testing:[2]

General population: genetic screening for HFE-HC is not recommended, as disease penetrance is low and only in few C282Y homozygotes will iron overload progress.

HFE testing should be considered in patients with unexplained chronic liver disease pre-selected for increased transferrin saturation.

HFE testing could be considered in patients with: Porphyria cutanea tarda Well-defined chondrocalcinosis Hepatocellular carcinoma Type 1 diabetes

HFE testing is not recommended in patients with unexplained arthritis or arthralgia or with type 2 diabetes.

Siblings of patients with HFE-related HHC should undergo screening, since they have a 25% chance of being susceptible. Serum ferritin and transferrin saturation should be assessed. Ideally HFE mutation analysis should be encouraged after appropriate genetic counselling.

Investigations and diagnosis

This involves assessment of iron overload, genetics and organ damage. These tests need careful interpretation.

Initial investigations

Assessment of iron stores: [2] Patients with suspected iron overload should first receive measurement of fasting transferrin saturation and serum ferritin, and HFE genetic testing should be performed only in those with increased transferrin saturation. Serum ferritin is the most widely used biochemical test for iron overload. Serum ferritin is a very sensitive test for iron overload in haemochromatosis and normal serum concentrations essentially rule out iron overload. However, ferritin has low specificity, as elevated values can be the result of a range of inflammatory, metabolic and neoplastic conditions such as diabetes mellitus, alcohol consumption and hepatocellular or other cell necrosis. Serum iron concentration and transferrin saturation do not quantitatively reflect body iron stores and should therefore not be used alone as markers of tissue iron overload.

Tests to exclude common causes of hyperferritinaemia: inflammation (check CRP), chronic alcohol consumption, liver cell necrosis (alanine aminotransferase), metabolic syndrome (blood pressure, BMI, triglycerides, glucose), anaemia (haemoglobin, mean cellular volume and further tests depending on ethnic background - eg, testing for sickle cell disease). [3]

LFTs.

Other tests, including endocrine investigations, may be indicated, depending on the clinical situation.

Investigations for other causes of abnormal liver function (eg, hepatitis serology) may be relevant.

Further investigations

Genetic testing: [2] HFE testing for the C282Y and H63D polymorphism should be carried out in all patients with otherwise unexplained increased serum ferritin and increased transferrin saturation. C282Y homozygosity is required for the diagnosis of HFE-HC, when iron stores are increased. Diagnosis of HFE haemochromatosis should not be based on C282Y homozygosity alone but requires evidence of increased iron stores.

Liver biopsy: In C282Y homozygote patients with increased iron stores, liver biopsy is no longer necessary to diagnose haemochromatosis. [2] It is now rarely required because genetic testing for HFE mutations is very reliable in the diagnosis of haemochromatosis in Caucasians and the majority of patients with haemochromatosis are now diagnosed at an early stage, well before permanent tissue damage occurs. [6] Liver biopsy may still be indicated - eg, to show whether iron stores are increased or not and in assessing liver fibrosis. [2] One large American study found that hepatic fibrosis and cirrhosis can exist without symptoms. [7]

MRI may be useful to detect and quantify hepatic iron excess and may also help to identify heterogeneous distribution of iron within the liver, differentiate parenchymal from mesenchymal iron overload and to detect small iron-free neoplastic lesions.[2]

Genetic tests interpretation[5, 8] C282Y homozygote - most will accumulate iron; only a minority will develop symptoms. Men are affected more often than women.

'Compound heterozygote' (C282Y with H63D) - most have normal iron levels. Moderate iron overload can develop. Severe iron overload may occur if there are other risk factors - eg, alcoholism or viral hepatitis.

H63D homozygote - most have normal iron levels. A few may develop iron overload - this may depend on other risk factors.

C282 heterozygote - about 10% of white people have this genotype; most have normal iron levels. Rarely, significant iron overload can occur (possibly due to another unknown haemochromatosis gene). [8]

H63D heterozygote - about 20% of white people have this genotype; iron overload is unlikely and if found, other causes should be considered.

No HFE mutation - the patient could still have HHC from an unrecognised gene (about 5% of UK HHC patients). Diagnosis is based on iron studies, liver biopsy and excluding other causes.

Differential diagnosis

Differential diagnosis of HHC:[3]

Management[2]

Patients with HFE-HC and evidence of excess iron should be treated with phlebotomy. Phlebotomy should be carried out by removing 400-500 ml of blood (200-250 mg iron) weekly or every two weeks. Adequate hydration before and after treatment and avoidance of vigorous physical activity for 24 hours after phlebotomy are recommended.

C282Y homozygotes without evidence for iron overload could be monitored annually and treatment instituted when the ferritin rises above normal.

Before the initiation of phlebotomy, patients with HFE-HC should be assessed for complications (including diabetes mellitus, joint disease, endocrine deficiency (hypothyroidism), heart failure, porphyria cutanea tarda and osteoporosis), which should be managed regardless of whether or not HC is the underlying cause and whether there is symptomatic relief or improvement during phlebotomy.

To minimise the risk of additional complications, patients with HFE-HC could be immunised against hepatitis A and B while iron-overloaded.

Liver transplantation:

Hepatic decompensation with ascites, spontaneous bacterial peritonitis, encephalopathy, variceal haemorrhage and early small tumour formation may require assessment for liver transplantation. Early reports on the outcome of HFE-HC after liver transplantation for HFE-HC have found that survival may be lower than in other groups. Survival for transplant patients is around 64% after one year and 34% after five years. [2]



Monitoring[3]

Serum ferritin is the main investigation used because it correlates with symptoms and the risk of complications.

When serum ferritin is less than 1000 μg/L the risk of serious liver damage is below 1%. Serum ferritin levels above 1000 μg/L are an indication for liver biopsy because of the risk of cirrhosis.

When a liver biopsy shows cirrhosis, periodic screening for hepatocellular carcinoma, using echography or magnetic resonance imaging, is essential.

Pregnancy

Iron supplements should not be given routinely to pregnant women with HFE-related HC.

Serum ferritin should be monitored.

Iron deficiency should be treated according to the usual guidelines applied to pregnancy.

If the ferritin is high, therapeutic phlebotomy should be deferred until the end of pregnancy unless there are cardiac or hepatic issues, in which case the appropriate specialist should be involved in the discussion of the positive and negative effects of treatment.

Diet

Compliance with phlebotomy will prevent iron overload.

Iron-containing vitamin preparations and iron-supplemented foods such as breakfast cereals should be avoided. Compliance with phlebotomy will prevent iron overload.

Tea drinking has been reported as possibly reducing the increase in iron stores in HC patients but this finding has not been confirmed.

Vitamin C has been reported to be potentially toxic in patients with iron overload. However, a single case report of a patient in whom vitamin C could have had a negative effect on cardiac function has led to the recommendation that it is prudent to limit ingestion of vitamin C supplements to 500 mg/day. [2]

Excess alcohol ingestion leads to increased hepatic damage in HFE-HC. There is a linear correlation between alcohol intake and serum iron indices and increased iron absorption in alcoholics.

Prognosis[3]