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URL of this page: https://medlineplus.gov/genetics/condition/x-linked-sideroblastic-anemia-and-ataxia/

X-linked sideroblastic anemia and ataxia

Description

X-linked sideroblastic anemia and ataxia is a rare condition that is characterized by a blood disorder called sideroblastic anemia and movement problems known as ataxia. This condition primarily occurs in males.

Anemia is defined by a shortage of healthy red blood cells. Sideroblastic anemia occurs when developing red blood cells called erythroblasts do not make enough hemoglobin, which is the protein that carries oxygen in the blood. People with X-linked sideroblastic anemia and ataxia have red blood cells that are smaller than normal (microcytic) and appear pale (hypochromic) because of the shortage of hemoglobin. The anemia seen in people with this condition is typically mild.

X-linked sideroblastic anemia and ataxia leads to an abnormal accumulation of iron in red blood cells. The iron-loaded red blood cells, which are present in bone marrow, are called ring sideroblasts.

X-linked sideroblastic anemia and ataxia causes problems with balance and coordination that appear early in life. Ataxia can make it difficult to sit, stand, and walk unassisted. People with this condition may find it difficult to make rapid, alternating movements (dysdiadochokinesia), such as tapping their foot. 

In addition to ataxia, people with this condition often have trouble coordinating movements that involve judging distance or scale (dysmetria), such as reaching out to grab an object. Affected individuals can also experience involuntary rhythmic shaking that worsens during movement (intention tremor). Mild speech difficulties (dysarthria) and abnormal eye movements have also been reported in some individuals with X-linked sideroblastic anemia and ataxia.

Frequency

X-linked sideroblastic anemia and ataxia is a rare disorder, although its exact prevalence is unknown.

Causes

Variants (also called mutations) in the ABCB7 gene cause X-linked sideroblastic anemia and ataxia. The ABCB7 gene provides instructions for making a protein that is critical for producing a component of hemoglobin called heme. Hemoglobin is vital for supplying oxygen to the entire body. The ABCB7 protein also plays a role in the formation of clusters of iron and sulfur atoms (Fe-S clusters). These clusters get incorporated into a variety of proteins that are necessary for many cell funcitons. The ABCB7 protein likely helps maintain an appropriate balance of iron (iron homeostasis) in erythroblasts. 

ABCB7 gene variants lead to changes in the structure of the ABCB7 protein, disrupting its usual roles in heme production and iron homeostasis. Anemia occurs when heme cannot be produced normally and red blood cells cannot make enough hemoglobin. It is likely that a lack of heme and proteins that contain Fe-S clusters disrupts cell functions, particularly in nerve cells, resulting in ataxia and the other movement problems seen in people with X-linked sideroblastic anemia with ataxia.

Learn more about the gene associated with X-linked sideroblastic anemia and ataxia

Inheritance

X-linked sideroblastic anemia and ataxia is inherited in an X-linked pattern. A condition is considered X-linked if the altered gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In males (who have only one X chromosome), a variant in the only copy of the gene in each cell is sufficient to cause the condition.  A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

In females (who have two copies of the X chromosome), one ABCB7 gene variant typically does not cause the health problems that are associated with X-linked sideroblastic anemia and ataxia; however, they may have abnormally small, pale red blood cells that can be detected with a blood test. 

Other Names for This Condition

  • SCAX6
  • X-linked sideroblastic anaemia with ataxia
  • X-linked spinocerebellar ataxia-6 with or without sideroblastic anemia
  • XLSA/A

Additional Information & Resources

Genetic Testing Information

Genetic and Rare Diseases Information Center

Patient Support and Advocacy Resources

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed

References

  • Bottomley SS. Congenital sideroblastic anemias. Curr Hematol Rep. 2006 Mar;5(1):41-9. Citation on PubMed
  • Camaschella C. Recent advances in the understanding of inherited sideroblastic anaemia. Br J Haematol. 2008 Oct;143(1):27-38. doi: 10.1111/j.1365-2141.2008.07290.x. Epub 2008 Jul 14. Citation on PubMed
  • Chiabrando D, Bertino F, Tolosano E. Hereditary Ataxia: A Focus on Heme Metabolism and Fe-S Cluster Biogenesis. Int J Mol Sci. 2020 May 26;21(11):3760. doi: 10.3390/ijms21113760. Citation on PubMed
  • Fleming MD. The genetics of inherited sideroblastic anemias. Semin Hematol. 2002 Oct;39(4):270-81. doi: 10.1053/shem.2002.35637. Citation on PubMed
  • Furuyama K, Kaneko K. Iron metabolism in erythroid cells and patients with congenital sideroblastic anemia. Int J Hematol. 2018 Jan;107(1):44-54. doi: 10.1007/s12185-017-2368-0. Epub 2017 Nov 14. Citation on PubMed
  • Hellier KD, Hatchwell E, Duncombe AS, Kew J, Hammans SR. X-linked sideroblastic anaemia with ataxia: another mitochondrial disease? J Neurol Neurosurg Psychiatry. 2001 Jan;70(1):65-9. doi: 10.1136/jnnp.70.1.65. Citation on PubMed or Free article on PubMed Central
  • Pagon RA, Bird TD, Detter JC, Pierce I. Hereditary sideroblastic anaemia and ataxia: an X linked recessive disorder. J Med Genet. 1985 Aug;22(4):267-73. doi: 10.1136/jmg.22.4.267. Citation on PubMed or Free article on PubMed Central
  • Protasova MS, Grigorenko AP, Tyazhelova TV, Andreeva TV, Reshetov DA, Gusev FE, Laptenko AE, Kuznetsova IL, Goltsov AY, Klyushnikov SA, Illarioshkin SN, Rogaev EI. Whole-genome sequencing identifies a novel ABCB7 gene mutation for X-linked congenital cerebellar ataxia in a large family of Mongolian ancestry. Eur J Hum Genet. 2016 Apr;24(4):550-5. doi: 10.1038/ejhg.2015.139. Epub 2015 Aug 5. Citation on PubMed
  • Xiong S, Jia Y, Li S, Huang P, Xiong J, Mao D, He Q, Liu L. The First Case Report of X-Linked Sideroblastic Anemia With Ataxia of Chinese Origin and Literature Review. Front Pediatr. 2021 Jul 20;9:692459. doi: 10.3389/fped.2021.692459. eCollection 2021. Citation on PubMed

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