Thiopurine S-Methyltransferase DeficiencySymptoms, Doctors, Treatments, Advances & More
Thiopurine S-Methyltransferase Deficiency Overview
Learn About Thiopurine S-Methyltransferase 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 autoimmune disorders, including Crohn's disease and rheumatoid arthritis, which occur when the immune system malfunctions. These drugs are also used to treat several forms of cancer, particularly cancers of blood-forming tissue (leukemias) and cancers of immune system cells (lymphomas). Additionally, thiopurine drugs are used in organ transplant recipients to help prevent the immune system from attacking the transplanted organ.
TPMT deficiency results from changes in the TPMT gene. This gene provides instructions for making the TPMT enzyme, which plays a critical role in breaking down (metabolizing) thiopurine drugs. Once inside the body, these drugs are converted to toxic compounds that kill immune system cells in the bone marrow. The TPMT enzyme "turns off" thiopurine drugs by breaking them down into inactive, nontoxic compounds. Changes in the TPMT gene reduce the stability and activity of the TPMT enzyme. Without enough of this enzyme, the drugs cannot be "turned off," so they stay in the body longer and continue to destroy cells unchecked. The resulting damage to the bone marrow leads to potentially life-threatening myelosuppression.
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.
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.
Piet Hooymans practices in Sittard, Netherlands. Hooymans is rated as a Distinguished expert by MediFind in the treatment of Thiopurine S-Methyltransferase Deficiency. Their top areas of expertise are Thiopurine S-Methyltransferase Deficiency, Viral Gastroenteritis, and Colitis.
Luc Derijks practices in Maastricht, Netherlands. Derijks is rated as a Distinguished expert by MediFind in the treatment of Thiopurine S-Methyltransferase Deficiency. Their top areas of expertise are Thiopurine S-Methyltransferase Deficiency, Viral Gastroenteritis, Crohn's Disease, and Hemorrhagic Proctocolitis.
Gregory A Robertson MD A Professional Medical Corp.
Gregory Robertson is a primary care provider, practicing in Internal Medicine in Newport Beach, California. Dr. Robertson has been practicing medicine for over 44 years and is rated as a Distinguished provider by MediFind in the treatment of Thiopurine S-Methyltransferase Deficiency. His top areas of expertise are Hyperphenylalaninemia Due to Dehydratase Deficiency, Complement Component 2 Deficiency, Thiopurine S-Methyltransferase Deficiency, Primary Immunodeficiency (PID), and Gastrostomy.
Published Date: April 01, 2015
Published By: National Institutes of Health