Sideroblastic anemia

Anemia characterized by the production of ringed sideroblasts instead of healthy red blood cells.

Other Names: Anemia sideroblastic

Sideroblastic anemia is a group of blood disorders characterized by an impaired ability of the bone marrow to produce normal red blood cells. In this condition, the iron inside red blood cells is inadequately used to make hemoglobin, despite normal amounts of iron. As a result, iron accumulates in the red blood cells, giving a ringed appearance to the nucleus (ringed sideroblast).

Types

Depending on the cause, it can be classified as hereditary (sometimes called congenital), acquired, and idiopathic (cause unknown).

Cause

Sideroblastic anemia can be caused by hereditary factors, acquired as part of an underlying condition or exposure to drugs or toxins, or the cause may be unknown (idiopathic).

Hereditary causes of sideroblastic anemia include:

• Mutations in the ALAS2, ABCB7, SCL19A2, GLRX5, and PSU1 genes
• Pearson syndrome
• Wolfram or DIDMOAD syndrome
• Mitochondrial SLC25A38
• Erythropoietic protoporphyria

Acquired causes of sideroblastic anemia include:

• Myelodysplastic syndrome
• SF3B1 - Splicing factor 3B subunit 1 mutations
• Nutritional deficiencies (copper, vitamin B6)
• Lead poisoning
• Zinc overdose
• Alcohol
• Drugs (anti-tuberculous agents, antibiotics, progesterone, chelators, busulfan)
• Hypothermia

Signs and symptoms

The signs and symptoms of sideroblastic anemia may include: fatigue, weakness, the sensation of a pounding or racing heart (palpitations), shortness of breath, headaches, irritability, and chest pain. Physical findings may include pale skin and/or a lemon-yellow colored tinge to the skin and rarely, a brownish discoloration caused by bleeding under the skin. Enlargement of the spleen (splenomegaly) and/or liver (hepatomegaly) may also occur. Rarely, in severe cases, acute leukemia can develop.

Diagnosis

The diagnostic workup for sideroblastic anemia may include blood work (complete blood count, peripheral smear, iron studies) and a bone marrow aspiration and/or biopsy. Additional studies that may be useful include imaging of the brain, such as MRI and genetic testing for known or suspected hereditary conditions associated with sideroblastic anemia.

Treatment

The treatment of sideroblastic anemia may differ depending on whether the underlying cause is inherited or acquired. For acquired cases, avoidance or removal of the toxin or causative medication may lead to recovery. Vitamin B6 (pyridoxine) therapy may be beneficial in both inherited and acquired forms. If vitamin B6 therapy is not effective, a blood transfusion can be useful, but since it has been known to worsen iron overload, the benefits and limitations of this option should be carefully considered. Rarely, when all other treatment methods have been exhausted, bone marrow transplantation may be utilized. While this therapy may offer the possibility of a cure, the complications associated with transplantation surgery must be considered. It is recommended that all individuals with sideroblastic anemia avoid zinc-containing supplements and the use of alcohol. Regular follow-up and care with a hematologist is important.

Prognosis

The prognosis of sideroblastic anemia varies depending on the underlying cause. For acquired cases, such as those associated with alcohol and drugs, there may not be long-term symptoms. Patients requiring transfusions, those with conditions unresponsive to pyridoxine and other therapies, and those with a myelodysplastic syndrome that develops into acute leukemia have a poorer prognosis. Major causes of death in cases of sideroblastic anemia are secondary hemochromatosis from transfusions and leukemia.

Thrombocytosis appears to be a relatively good prognostic sign. Patients with no need for blood transfusions are very likely to be long-term survivors, whereas those who become transfusion dependent are at risk of death from the complications of secondary hemochromatosis.

NIH genetic and rare disease info

• NIH info on Sideroblastic anemia

Sideroblastic anemia is a rare disease.

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