How common is TPMT deficiency?
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Studies suggest that less than 1 percent of individuals in the general population have TPMT deficiency. Another 11 percent have moderately reduced levels of TPMT activity that increase their risk of hematopoietic toxicity with thiopurine drug treatment.
What happens when TPMT levels are low?
Patients with low or absent TPMT activity metabolize the drugs more slowly and have higher thioguanine nucleotide concentrations, increasing the risk of developing severe, life-threatening myelosupression if conventional doses are given.
What is TPMT genotype test?
TPMT genetic test (genotype)—an alternative test to TPMT enzyme activity level is a genetic test that can identify genetic variations in the TPMT gene. This genetic test identifies individual genetic differences associated with risk for thiopurine toxicity. Each person has two copies of the TPMT gene.
What percentage of the population has normal or high TPMT activity?
Approximately 89%–90% of the general Caucasian population has high (normal) TPMT activity, which corresponds with homozygous expression of TPMT∗1.
What is the normal function of the TPMT enzyme?
Normal Function The TPMT gene provides instructions for making an enzyme called thiopurine S-methyltransferase (TPMT). This enzyme carries out a specific chemical reaction called S-methylation of a group of molecules known as aromatic and heterocyclic sulphydryl compounds.
Why is TPMT important?
Therefore, the TPMT genetic polymorphism is a significant factor responsible for serious adverse drug reactions (myelosuppression) in patients treated with thiopurines and may also contribute to individual variation in therapeutic efficacy [Article:15784872].
What is the role of TPMT?
The TPMT gene provides instructions for making an enzyme called thiopurine S-methyltransferase (TPMT). This enzyme carries out a specific chemical reaction called S-methylation of a group of molecules known as aromatic and heterocyclic sulphydryl compounds.
Where is the TPMT gene located?
Thiopurine methyltransferase or thiopurine S-methyltransferase (TPMT) is an enzyme that in humans is encoded by the TPMT gene. A pseudogene for this locus is located on chromosome 18q….Thiopurine methyltransferase.
TPMT | ||
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Location (UCSC) | Chr 6: 18.13 – 18.16 Mb | Chr 13: 47.18 – 47.2 Mb |
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What is the prevalence of TPMT deficiency in the US?
Studies suggest that less than 1 percent of individuals in the general population have TPMT deficiency. Another 11 percent have moderately reduced levels of TPMT activity that increase their risk of hematopoietic toxicity with thiopurine drug treatment. TPMT deficiency results from changes in the TPMT gene.
What is thiopurine S-methyltransferase (TPMT) deficiency?
Thiopurine S-methyltransferase (TPMT) deficiency is a condition characterized by significantly reduced activity of an enzyme that helps the body process drugs called thiopurines. These drugs, which include 6-thioguanine, 6-mercaptopurine, and azathioprine, inhibit (suppress) the body’s immune system. Thiopurine drugs are used to treat some
What is the significance of TPMT*3C?
TPMT*3C and TPMT*12 are the key determinants of 6-mercaptopurine-mediated hematological toxicity in acute lymphoblastic leukemia patients As expected TPMT was the main cause of severe hematotoxicity in 31% of patients, who were either TPMT deficient (10%) or heterozygous carriers of TPMT variants (21%).
Is TPMT a high or low activity gene?
The activity of the TPMT enzyme is inherited in a pattern described as autosomal codominant. Codominance means that two different versions of the gene are active (expressed), and both versions influence the genetic trait. The TPMT gene can be classified as either low-activity or high-activity.