CARBAMAZEPINE HYPERSENSITIVITY — HLA-B*15:02

Carbamazepine Hypersensitivity — HLA allele-specific reactions causing Stevens-Johnson syndrome and toxic epidermal necrolysis, with up to 30% mortality, from the world's most prescribed anticonvulsant.

Whole genome sequencing provides complete HLA typing — covering HLA-B*15:02 (critical for Asian populations) and HLA-A*31:01 (critical for European populations) in a single result — guiding the most important prescribing decision in epilepsy pharmacogenomics.

HLA-B
HLA-A

About this condition

Carbamazepine Hypersensitivity — HLA-B*15:02

Carbamazepine (Tegretol) is one of the most widely prescribed anticonvulsants for focal epilepsy, trigeminal neuralgia, and bipolar disorder. In a subset of patients, carbamazepine triggers severe cutaneous adverse reactions: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) — immune-mediated blistering reactions involving widespread skin and mucosal membrane detachment, with extensive tissue loss, sepsis risk, and mortality rates of 5-30%. These reactions are not dose-dependent and occur in HLA allele-specific patterns that allow pre-treatment prediction.

Two HLA alleles have been validated as pharmacogenomic biomarkers for carbamazepine SJS/TEN in distinct populations. HLA-B*15:02 is strongly associated with SJS/TEN risk in Han Chinese, Thai, Malaysian, Vietnamese, and other Southeast Asian populations — allele frequency ranging from 5-15% in affected ethnic groups, essentially absent in European populations. HLA-B*15:02 carriers in Asian populations who receive carbamazepine have approximately a 5-10% risk of SJS/TEN, compared to <0.1% in non-carriers. HLA-A*31:01 is associated with carbamazepine hypersensitivity (including SJS/TEN but also milder maculopapular exanthema and drug reaction with eosinophilia and systemic symptoms/DRESS) in Europeans, Japanese, and other populations where HLA-B*15:02 is rare. HLA-A*31:01 frequency is approximately 2-5% in European populations.

The FDA added a warning to carbamazepine in 2007 recommending that patients of Asian ancestry be tested for HLA-B*15:02 before initiating carbamazepine therapy. CPIC provides Level A guidelines for carbamazepine and both HLA-B*15:02 and HLA-A*31:01. Alternative anticonvulsants — lamotrigine, levetiracetam, phenytoin with appropriate HLA consideration, oxcarbazepine — can be prescribed to confirmed HLA risk carriers. The urgency of pre-treatment screening is underscored by the irreversibility of SJS/TEN — once the reaction begins, its course cannot be aborted, and the outcome depends only on early drug cessation and intensive supportive care.

HLA-B*15:02 is the critical allele in Southeast Asian populations. HLA-A*31:01 is the critical allele in European, Japanese, and other populations. Both alleles must be evaluated for complete carbamazepine pharmacogenomic risk assessment across all ancestries.

Gene locus: HLA-B and HLA-A (6p21.33)

Commercial tests exist for HLA-B15:02 alone. What whole genome sequencing adds is comprehensive HLA typing — covering HLA-A31:01, HLA-B58:01 (allopurinol), HLA-B57:01 (abacavir), and all other pharmacogenomically relevant HLA alleles in a single test.

Testing only HLA-B15:02 misses European carbamazepine hypersensitivity risk from HLA-A31:01

Commercial point-of-care HLA-B*15:02 tests were developed specifically for Asian patient populations prescribed carbamazepine. When applied in European or mixed-ancestry patient populations, a negative HLA-B*15:02 result is correct but incomplete — it does not address HLA-A*31:01, the primary carbamazepine hypersensitivity allele in Europeans. CPIC recommends testing for HLA-A*31:01 in all non-Asian patients being considered for carbamazepine. A single HLA-B*15:02-only test misses all HLA-A*31:01 risk. Whole genome sequencing performs complete HLA class I typing at 4-digit field resolution, covering all pharmacogenomically relevant HLA alleles simultaneously.

Complete HLA typing is a permanent pharmacogenomic asset covering carbamazepine, allopurinol, abacavir, and future drugs

The pharmacogenomic HLA landscape extends beyond carbamazepine. HLA-B*58:01 predicts allopurinol-induced SJS/TEN (particularly in Han Chinese and Korean populations). HLA-B*57:01 predicts abacavir hypersensitivity. HLA-A*31:01 also predicts oxcarbazepine and phenytoin hypersensitivity in some populations. A patient who requires anti-epileptic or gout medication management may encounter multiple of these prescribing decisions over their lifetime. Complete HLA typing from whole genome sequencing answers all of these questions simultaneously and permanently, with the result stored in the medical record for use at every future prescribing encounter.

Carbamazepine Hypersensitivity — HLA allele-specific reactions causing Stevens-Johnson syndrome and toxic epidermal necrolysis, with up to 30% mortality, from the world's most prescribed anticonvulsant.

Carbamazepine Hypersensitivity — HLA-B*15:02

Commercial tests exist for HLA-B*15:02 alone. What whole genome sequencing adds is comprehensive HLA typing — covering HLA-A*31:01, HLA-B*58:01 (allopurinol), HLA-B*57:01 (abacavir), and all other pharmacogenomically relevant HLA alleles in a single test.

Testing only HLA-B*15:02 misses European carbamazepine hypersensitivity risk from HLA-A*31:01

Complete HLA typing is a permanent pharmacogenomic asset covering carbamazepine, allopurinol, abacavir, and future drugs

Others in Pharmacogenomics

One test. A lifetime of answers.

Commercial tests exist for HLA-B15:02 alone. What whole genome sequencing adds is comprehensive HLA typing — covering HLA-A31:01, HLA-B58:01 (allopurinol), HLA-B57:01 (abacavir), and all other pharmacogenomically relevant HLA alleles in a single test.

Testing only HLA-B15:02 misses European carbamazepine hypersensitivity risk from HLA-A31:01