Sideroblastic Anemia

Sideroblastic anemia (SA) is a rare blood disorder that affects how your body makes red blood cells. If you have SA, you have anemia, meaning your body doesn’t make enough healthy red blood cells. You can also have too much iron in your system because your body’s not using it to make red blood cells.

With SA, there’s a problem with how your red blood cells use iron to make hemoglobin. Hemoglobin is a key protein red blood cells need to do their main job — carrying oxygen throughout your body. Not having enough red blood cells can leave you feeling tired and weak.

Meanwhile, the unused iron builds up inside developing red blood cells, forming abnormal cells called ring sideroblasts. A sideroblast is an immature red blood cell with iron forming a ring around its center (nucleus). The rings are a sign the cells are storing iron instead of using it. This can lead to iron overload. The iron that builds up is responsible for many of the major medical issues this condition may cause.

Types of this condition

People either inherit or acquire sideroblastic anemia:

• Congenital (inherited): You may be born with a faulty gene (variant) that disrupts how red blood cells use iron. The most common type is called X-linked sideroblastic anemia.
• Acquired: Most people with SA get it at some point in their lives. Sometimes, it’s a sign of myelodysplastic syndrome (MDS). Other times, it’s a sign of something you can reverse, like a mineral deficiency. You can often cure SA that comes from a reversible cause. 

Symptoms of sideroblastic anemia

Like many forms of anemia, sideroblastic symptoms may include:

• Fatigue
• Headaches
• Heart palpitations
• Shortness of breath

People with some forms of SA may have more symptoms, like:

• Bronze-colored skin (a possible sign your body is storing too much iron)
• Dull pain or tenderness in the upper left part of your abdomen (a sign of an enlarged spleen)
• Muscle weakness
• Problems with coordination
• Slow reflexes
• Stunted growth

Symptoms range from mild to severe. This is why some people born with this condition may not have major issues until they’re older and symptoms worsen.

Sideroblastic anemia causes

This condition happens when red blood cells can’t use iron to make hemoglobin. This keeps them from working as they should to carry oxygen.

The cause depends on the type.

Congenital SA

With inherited sideroblastic anemia, you’re born with an abnormal gene. The gene contains errors that impact one or more of the processes that allow red blood cells to use iron. These genes are usually on your X chromosome. The gene that’s usually impacted is the ALAS2 gene. But there are lots of gene variants linked to congenital SA.

Acquired SA

Acquired SA is either primary or secondary. Primary SA happens as part of a bone marrow condition called myelodysplastic syndrome (MDS). MDS involves a gene change (mutation) that happens at some point in your life. It causes your body to make abnormal blood cells. Secondary SA can result from causes like: 

• Alcohol overuse: Heavy alcohol use can interfere with how your body makes red blood cells.
• Heavy metal poisoning: This includes lead poisoning and arsenic poisoning.
• Vitamin B deficiency: Vitamin B6 helps your body make heme. Red blood cells use heme to make the protein hemoglobin.
• Copper deficiency: Copper helps create an enzyme that protects against iron overload.
• Zinc overdose: Too much zinc affects how your body uses iron. Taking too many zinc supplements puts you at risk of a copper deficiency.
• Medications: The drugs most likely to cause sideroblastic anemia are the antibiotics chloramphenicol, linezolid and isoniazid.

Complications of this condition

Babies born with sideroblastic anemia may have life-threatening medical issues stemming from iron overload. Adults who develop sideroblastic anemia may develop heart disease or cirrhosis if too much iron builds up.

How doctors diagnose this condition

Your healthcare provider will look at your red blood cells beneath a microscope. Finding ring sideroblasts in your bone marrow is a key sign of this condition. Other tests can reveal the type and the cause. They include:

• Bone marrow aspiration
• Complete blood count
• Iron studies
• Peripheral blood smear
• Genetic testing 

How is it treated?

Treatment depends on the type of sideroblastic anemia and its cause.

For secondary forms of acquired SA, the condition usually improves once you address the cause. This may involve switching medications or treating a vitamin B or copper deficiency. It may involve giving up alcohol. Reversing the effects may take as little as a few weeks or as long as a few months.

Your healthcare provider will work with you to manage congenital SA or sideroblastic anemia linked to MDS. Options include:

• Anemia medicines: Certain medicines can help your body make red blood cells that use iron correctly. They include erythropoietin-stimulating agents and luspatercept.
• Blood transfusions: With severe anemia, you may need regular blood transfusions. You’ll get healthy red blood cells from a donor to boost your counts.
• Stem cell transplants: This procedure replaces your stem cells (the early form of your blood cells) with healthy ones from a donor. It’s a possible cure for severe SA. But it’s an intensive procedure that comes with major risks.
• Chelation therapy: You’ll take medicine to remove excess iron from your body. You may need it if you’re at risk of iron overload. Iron overload can happen because of the condition itself or from repeated blood transfusions.
• Phlebotomy therapy (bloodletting): This treatment also removes iron from your body. It involves a provider removing a small amount of blood (about a pint). This option is usually only for people who don’t have significant anemia.

What can I expect if I have this condition?

Your outcome depends on the kind of sideroblastic anemia you have. For instance, some acquired forms can improve or resolve if the causes are treatable.

The outlook isn’t as straightforward if you have MDS or a congenital form of SA. Your experience depends on things like how severe your condition is and whether you’re at risk of iron overload.

You may need to work with your healthcare provider long-term to keep your red blood cells and iron at safe levels. You may need regular blood tests to monitor your health.

If you have congenital SA, it’s a good idea to talk to a genetic counselor. They can help you know how likely it is that you’ll pass the condition on to your biological children.

Can this be prevented?

You can’t prevent SA related to your genes. But if you or a relative has congenital SA, you may want to ask your healthcare provider about genetic testing.

There are things you can do to prevent some forms of acquired SA. If you take zinc supplements to cope with common colds, make sure you’re taking a safe dose. You can also limit your alcohol intake.

What is the most common cause of sideroblastic anemia?

Most sideroblastic anemias are acquired. Some are linked to bone marrow conditions like MDS. Others are caused by reversible factors like medications, alcohol use or nutrient deficiencies.

What is the difference between iron-deficiency anemia and sideroblastic anemia?

Iron-deficiency anemia is the most common type of anemia, while sideroblastic anemia is rare. Unlike with iron-deficiency anemia, SA doesn’t involve not having enough iron in your body. Instead, something prevents red blood cells from using the iron to make hemoglobin.