Type 4 genetic haemochromatosis is caused by genetic changes (mutations) to the SLC40A1 gene. The disease is inherited in an autosomal dominant manner, which differs from the other types of the condition.

Mutations of the SLC40A1 gene result in low levels of functional ferroportin (a protein that transport iron from the inside of a cell to the outside of the cell). The lack of this protein ultimately results in the abnormal accumulation of iron in the cells and tissues of the body.

Haemochromatosis type 4 can be divided into two subtypes:

• haemochromatosis type 4A
• haemochromatosis type 4B

People with haemochromatosis type 4A might not have any symptoms of the disease. Other individuals with haemochromatosis type 4B might experience the same signs and / or symptoms of the type 1 haemochromatosis.

Symptoms of haemochromatosis type 4B can begin anytime from childhood to adulthood.

The diagnosis is suspected when is observed signs or symptoms of the disease. The diagnosis can be confirmed with genetic testing.

Haemochromatosis type 4 is a disease that shows reduced penetrance. This means that some people with the mutation in the SLC40A1 gene never experience symptoms of the disease.

When a person with haemochromatosis type 4 has children, each child has a:

• 50% chance to inherit the pathogenic variant in the SLC40A1 gene;
• 50% chance to inherit the working copy of the SLC40A1, meaning he or she will not develop symptoms of haemochromatosis type 4.

Treatment for haemochromatosis type 4 depends on whether the affected individual has type 4A or type 4B. People with haemochromatosis type 4B can be treated similarly to people who have other types of haemochromatosis. Treatment involves phlebotomy (removal of blood).

Treatment for people with haemochromatosis type 4A typically does not involve phlebotomy. This is because people with haemochromatosis type 4A may develop low levels of red blood cells (anaemia) if they receive phlebotomy treatments. It is important regular monitoring with blood tests to determine if they are experiencing symptoms of the disease and how best the disease may be treated.