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Thiopurine S methyltranferase deficiency

Other Names for this Disease
  • 6-mercaptopurine sensitivity
  • Thiopurine methyltransferase deficiency
  • Thiopurines, poor metabolism of
  • TPMT deficiency
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Thiopurine S-methyltransferase deficiency is an autosomal recessive disorder that affects the body's ability to metabolize thiopurine drugs. Thiopurine S-methyltransferase (TPMT) is an enzyme that the body uses to break down thiopurine drugs. Thiopurine S-methyltransferase deficiency patients have a mutation in either one or both copies of the TPMT gene that causes reduced enzyme activity and difficulties breaking down thiopurine drugs. Affected individuals are at a high risk of experiencing bone marrow damage if they take thiopurine drugs. Many patients recover from the bone marrow damage once thiopurine drug use is stopped. However when the bone marrow is damaged, infections can cause serious health problems and may be life-threatening. To reduce the risk of bone marrow damage, thiopurine therapy should be lowered based on how many mutations a patient has in the TPMT gene. [1]
Last updated: 8/29/2012


  1. Barlow N. Thiopurine S-methyltransferase deficiency. Orphanet. May 2012; Accessed 8/29/2012.
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In Depth Information

  • The Online Mendelian Inheritance in Man (OMIM) is an catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Thiopurine S methyltranferase deficiency. Click on the link to view a sample search on this topic.