Introduction

Hemochromatosis is a condition characterised by the abnormal accumulation of iron in the body, leading to potential damage in various organs. It predominantly affects individuals of Northern European descent.

There are several types of hemochromatosis, each with distinct causes:

1. Hereditary hemochromatosis - This is inherited and has several types:
   • Type 1 - Caused by mutations in the HFE gene
   • Type 2a - Caused by mutations in the HJV gene
   • Type 2b - Caused by mutations in the HAMP gene.
   • Type 3 - Caused by mutations in the TFR2 gene
   • Type 4 (Ferroportin disease) - Caused by mutations in the SLC40A1 gene
2. Acquired hemochromatosis - Mainly results from other conditions, such as sickle cell anaemia or thalassemia
3. Neonatal hemochromatosis - A rare, severe form that presents in newborns and is often associated with maternal conditions^1,2,3

This article focuses on differentiating between hereditary hemochromatosis type 1 and type 4. Although both types lead to iron overload, they differ in their genetic causes and mechanisms of iron accumulation. Accurate differential diagnosis is crucial for effective management and for preventing complications associated with iron overload.

Genetic background and pathophysiology

Ferroportin disease

Ferroportin disease is caused by mutations in the SLC40A1 gene, which encodes the protein ferroportin. Ferroportin is a cell membrane protein responsible for exporting iron from inside cells into the bloodstream, allowing iron to be transported to various tissues. Mutations in SLC40A1 impair ferroportin's function, hindering its ability to release iron from cells. Consequently, iron accumulates in the cells, leading to iron overload in key organs such as the liver, spleen, and bone marrow. This condition is inherited in an autosomal dominant pattern, meaning that a single mutated copy of the SLC40A1 gene from either parent is sufficient to cause the disorder.^1,4

Hereditary hemochromatosis type 1 

Hereditary hemochromatosis type 1 is associated with mutations in the HFE gene, which encodes the HFE protein. The HFE protein regulates the production of hepcidin, a hormone crucial for controlling iron absorption. Mutations in the HFE gene disrupt the normal function of the HFE protein. This disruption impairs the regulation of hepcidin, leading to excessive absorption of dietary iron from the gastrointestinal tract. The resulting systemic iron overload causes iron to be deposited in various organs, including the liver, heart, pancreas, endocrine glands, and joints. Unlike ferroportin disease, hereditary hemochromatosis type 1 is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated HFE gene (one from each parent) to exhibit the disease.^2,5

Clinical manifestation

Ferroportin disease

• Liver disease - Iron overload in the liver can lead to progressive liver damage typically confined to a pre-cirrhotic stage, characterised by varying degrees of liver fibrosis
• Marginal anaemia - Patients may exhibit mild or marginal anaemia due to the body's inability to regulate iron properly
• Elevated serum ferritin - Ferritin, a blood protein that stores iron, is often significantly increased in ferroportin disease. This elevation results from the accumulation of iron in tissues due to the body’s impaired iron export mechanism
• Low transferrin saturation - Transferrin saturation measures the percentage of transferrin, an iron-binding protein, that is occupied by iron. In ferroportin disease, transferrin saturation is typically low, as excess iron cannot be properly exported from cells, leading to decreased iron availability for transferrin binding in the blood^1,6

Hereditary hemochromatosis type 1

• Liver cirrhosis - Iron accumulation in the liver can cause significant damage, leading to cirrhosis, characterised by liver scarring, impaired liver function, and an increased risk of liver cancer
• Skin pigmentation - Iron deposition in the skin can lead to a distinctive slate-grey or bronze discolouration
• Diabetes - Iron deposition in the pancreas impairs insulin production and glucose metabolism, leading to diabetes
• Elevated serum ferritin - Elevated serum ferritin levels are a hallmark of hereditary hemochromatosis, reflecting excess iron stores in the body
• Elevated transferrin saturation - Increased transferrin saturation is due to the high availability of iron in the bloodstream, resulting from excessive iron absorption and inadequate regulation^5,7

Diagnosis

• Genetic testing - Identifying specific mutations is crucial for confirming the diagnosis of either ferroportin disease or hereditary hemochromatosis type 1:
  • SLC40A1 - For ferroportin disease, genetic testing focuses on identifying mutations in the SLC40A1 gene, which encodes the ferroportin protein
  • HFE - For hereditary hemochromatosis type 1, genetic testing identifies mutations in the HFE gene
• Blood tests - Measuring serum ferritin and transferrin saturation levels can aid in distinguishing between ferroportin disease and hereditary hemochromatosis type 1
• Serum Ferritin - Elevated in both conditions, but the degree of elevation and associated symptoms can vary
• Transferrin saturation - Typically low in ferroportin disease and elevated in hereditary hemochromatosis type 1
• Liver biopsy - A liver biopsy can assess the extent of liver damage, such as fibrosis or cirrhosis, providing insight into the degree of iron overload and its impact on liver function^3,5

Management and treatment

While there is no cure for ferroportin disease or hereditary hemochromatosis type 1, several management strategies can help control the conditions:^1,5

• Phlebotomy - This is the primary treatment for both ferroportin disease and hereditary hemochromatosis type 1. It involves the periodic removal of blood to reduce iron levels in the body. Regular phlebotomy sessions are typically required until iron stores are reduced to safe levels, followed by ongoing maintenance therapy
• Chelation therapy - Iron chelation therapy is generally used when phlebotomy is not appropriate. Chelating agents, such as deferoxamine, deferasirox, or deferiprone, help remove excess iron from the body
• Dietary modifications - Patients are advised to make dietary changes to manage iron levels:
  • Avoid iron-rich foods
  • Reduce vitamin C intake, as it enhances iron absorption
  • Avoid iron supplements unless specifically prescribed

FAQs

What is the main difference between Ferroportin Disease and Hereditary Hemochromatosis Type 1?

Ferroportin disease is caused by mutations in the SLC40A1 gene, leading to impaired iron export from cells and iron accumulation in the liver, spleen, and bone marrow. In contrast, hereditary hemochromatosis type 1 is due to mutations in the HFE gene, resulting in excessive iron absorption from the diet and subsequent iron overload in various organs.

What treatments are available for Ferroportin Disease and Hereditary Hemochromatosis Type 1?

Treatments for both conditions include phlebotomy to reduce iron levels, chelation therapy if phlebotomy is not feasible, and dietary modifications to manage iron intake. 

Can dietary changes help manage iron overload in these conditions?

Yes, dietary modifications can be beneficial. For both ferroportin disease and hereditary hemochromatosis type 1, patients are advised to avoid iron-rich foods, reduce vitamin C intake (which enhances iron absorption), and avoid iron supplements unless specifically prescribed.

Summary

Ferroportin disease and hereditary hemochromatosis type 1, though both result in iron overload, differ significantly in their causes and manifestations. Ferroportin disease, due to mutations in the SLC40A1 gene, impairs iron export from cells, leading to iron accumulation in the liver, spleen, and bone marrow, often presenting with elevated serum ferritin and low transferrin saturation. In contrast, hereditary hemochromatosis type 1, caused by mutations in the HFE gene, results in excessive iron absorption from the diet, with symptoms including liver cirrhosis, skin pigmentation, and diabetes, marked by elevated serum ferritin and transferrin saturation. Accurate diagnosis of these conditions requires genetic testing and blood analysis. Management strategies for both ferroportin disease and hereditary hemochromatosis type 1 include phlebotomy, chelation therapy, and dietary modifications to control iron levels and prevent complications.