Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are life-threatening conditions affecting skin and mucous membranes. Although the incidence of SJS and TEN is low (0.4-6 cases per million persons per year) the incidence is increased in certain ethnic groups and mortality rates are high (Tangamornsuksan et al., 2013). Mortality rates are < 5 % for SJS and > 30 % for TEN, with sepsis being the most frequent cause of death (Leckband et al., 2013). Eighty percent of SJS and TEN is due to medication use and carbamazepine is the most common cause (Tangamornsuksan et al., 2013). SJS/TEN appears usually within the first 3 months after the start of the medication (Leckband et al., 2013). Genetic testing is highly recommended before carbamazepine is administered to patients from specific Asian regions including China, Taiwan, Thailand, Malaysia, Oceania and India. Patients carrying HLA-B*1502 are at strongly increased risk for life treatening carbamazepine-induced Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). E.g.: Han-Chinese living in Taiwan: The odds ratio if positive for HLA-B*1502 for developing carbamazepine-induced Stevens-Johnson syndrome/toxic epidermal necrolysis was 2504 (95% CI: 126−49,522) (Ferrel, 2008). HLA-B*1502 is rare among Caucasians or Japanese.
A systematic review with outcome of carbamazepine-induced SJS and TEN shows that the 'summary OR' for the relationship between HLA-B*1502 and carbamazepine-induced SJS and TEN was 79.84 (95% CI, 28.45-224.06). Han-Chinese (115.32; 18.17-732.13), Thais (54.43; 16.28-181.96), and Malaysians (221.00; 3.85-12 694.65). Among individuals of Caucasian and Japanese origine, no patients with SJS or TEN were carriers of the HLA-B*1502 allele (Tangamornsuksan et al., 2013).
- HLA-B*1502 % in some major populations in Asia:
- Singapore 11.6%
Han Chinese 10.2%
Malay 8.4%
Thai 6.1%
India Khandesh Pawra 6.0%
Filipino 5.3%
India North Hindi 2.0%
India Mumbai Marathas 1.0%
Korean 0.5%
(Ferrel, 2008, González-Galarza,2015 and http://www.allelefrequencies.net)
Check also: World map: interethnic differences in population prevalence of the HLA-B*1502 allele