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Disease Profile

Thiopurine S methyltranferase deficiency

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

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ICD-10

#N/A

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

TPMT deficiency; Thiopurines, poor metabolism of; Thiopurine methyltransferase deficiency;

Categories

Congenital and Genetic Diseases; Metabolic disorders

Summary

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]

Symptoms

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
Percent of people who have these symptoms is not available through HPO
Abnormality of blood and blood-forming tissues
0001871
Abnormality of metabolism/homeostasis
Laboratory abnormality
Metabolism abnormality

[ more ]

0001939
Autosomal recessive inheritance
0000007

Diagnosis

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
  • Orphanet lists international laboratories offering diagnostic testing for this condition.

Treatment

The National Institutes of Health Clinical Pharmacogenomics Implementation Consortium isssued recommendations on how to manage patients with TPMT deficiency. They recommend that patients with one TPMT gene change reduce thiopurine doses by about 30-70%. Patients with two TPMT gene changes should reduce thiopurine doses by at least 10-fold. The frequency of doses should also be reduced from daily to three times per week.[2]

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Thiopurine S methyltranferase deficiency. This website is maintained by the National Library of Medicine.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a 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.

References

  1. Barlow N. Thiopurine S-methyltransferase deficiency. Orphanet. May 2012; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=3315. Accessed 8/29/2012.
  2. Relling MV, Gardner EE, Sandborn WJ et al. Clinical Pharmacogenetics Implementation Consortium guidelines for thiopurine methyltransferase genotype and thiopurine dosing. Clin Pharmacol Ther. March 2011; 3:387-391. https://www.ncbi.nlm.nih.gov/pubmed/21270794. Accessed 8/29/2012.

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