Inflammatory bowel disease
bowel disease (IBD) is a group of inflammatory conditions of the and small , with disease and (UC) being the principal types. Crohn's disease affects the small intestine and large intestine, as well as the mouth, , stomach and the anus, whereas UC primarily affects the colon and the .
Underlined words are explained — tap any of them.
The sections below are general education drawn from public guidelines (NHS, Mayo, CPIC, WHO, ICMR). They are not individually reviewed by a clinician and are not medical advice — always talk to a doctor about your own health.
Genes that change how certain drugs work — and that differ in South Asians. This is education, not a dosing tool; genotype-guided prescribing is a clinician decision.
Thiopurines are strong drugs that your body has to clear away safely using a cleanup called . If your gene makes little or none of it, the drug builds up and can crash your blood counts - so people with this gene version need a much smaller dose or a different drug.
South Asian signal: NUDT15 c.415C>T (rs116855232, the *3 defining variant) has a minor allele frequency of ~6.7% in South Asians per gnomAD (vs ~10.5% in East Asians) - far higher than TPMT risk alleles, which are only ~1.4-2.5% in Asians. In Indian paediatric ALL patients, NUDT15 variants were found in 16.7% vs TPMT*3C in only 3.3% (PMC12722899).
Prescriber note: In South Asian patients, NUDT15 c.415C>T is the higher-yield thiopurine safety test than TPMT; a heterozygous (intermediate) or homozygous (poor metaboliser) result mandates a reduced starting dose or alternative agent with close CBC monitoring. CPIC recommends reducing the thiopurine starting dose for NUDT15 intermediate metabolisers and substantially reducing or avoiding thiopurines for poor metabolisers, to prevent life-threatening myelosuppression; in Asians, NUDT15 predicts toxicity better than TPMT.
Not a dosing tool. Genotype-guided prescribing is a clinician decision; genotyping access in India is limited.
is a second cleanup for the same family of drugs. Some people are born making very little of it, so the medicine piles up and harms the bone . Testing it alongside tells the doctor how much drug is safe.
South Asian signal: TPMT no-function alleles are relatively uncommon in South/East Asians (~1.4-2.5%), notably lower than in Europeans and Africans; in Indian paediatric ALL, TPMT*3C heterozygosity was ~3.3% vs NUDT15 variants at 16.7% (PMC12722899). This is why NUDT15 carries more of the toxicity signal in this population.
Prescriber note: Test TPMT together with NUDT15 before starting thiopurines; a normal TPMT does not reassure in a South Asian patient because NUDT15 deficiency is the more common cause of toxicity here. Let the more deficient of the two genes govern dosing. CPIC recommends reduced thiopurine dosing for TPMT intermediate metabolisers and major dose reduction or avoidance for poor metabolisers; TPMT and NUDT15 are interpreted jointly, with the more severe phenotype driving the decision.
Not a dosing tool. Genotype-guided prescribing is a clinician decision; genotyping access in India is limited.