1. Rapid Communication
HLA-B⁄
1502 is associated with carbamazepine induced Stevens–Johnson
syndrome in North Indian population
Ritu Aggarwal a,⇑
, Madhulika Sharma a
, Manish Modi b
, Vivek kumar Garg b
, Manilla Salaria a
a
Department of Immunopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
b
Department of Neurology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
a r t i c l e i n f o
Article history:
Received 8 July 2014
Accepted 27 September 2014
Available online xxxx
Keywords:
HLA
India
PCR
Pharmacogenetics
Toxic epidermal necrolysis
a b s t r a c t
The evidence of association between HLA-B⁄
1502 and anticonvulsant induced Stevens–Johnson
syndrome (SJS) and toxic epidermal necrolysis (TEN) from the Indian population is scant. Patients with
a history of SJS/TEN secondary to carbamazepine or phenytoin were enrolled. The control group com-
prised of patients who had received carbamazepine/phenytoin for P6 months without any adverse cuta-
neous event. Low-resolution DNA typing for HLA-B and high resolution HLA-B⁄
15 typing was performed.
Seventeen patients with history of SJS/TEN secondary to carbamazepine (9) or phenytoin (8) and 50 tol-
erant controls (carbamazepine-37; phenytoin-13) were enrolled. The mean age of patients and controls
was 33.9 ± 11.6 and 28.1 ± 9.9 years, respectively. HLA-B⁄
1502 was observed in 2/9 (22.2%) carbamaze-
pine-SJS/TEN patients and none of the 37 carbamazepine tolerant controls (p = 0.035). HLA-B⁄
1502 was
not observed in any of the 8 phenytoin-SJS/TEN patients or the 13 phenytoin tolerant controls. Our data
suggests that HLA-B⁄
1502 is a risk factor for carbamazepine induced SJS/TEN. Therefore, HLA-B⁄
1502
testing should be performed prior to initiating carbamazepine in North Indian population.
Ó 2014 Published by Elsevier Inc. on behalf of American Society for Histocompatibility and
Immunogenetics.
1. Introduction
Adverse drug reaction as defined by WHO, is a noxious and
unintended response to a drug that occurs at a dose normally used
in man [1]. They can range from mild maculopapular exanthema to
life threatening conditions, including, Stevens–Johnson syndrome
(SJS) and toxic epidermal necrolysis (TEN). In a recent systematic
review of the published evidence of drug-induced SJS and TEN in
Indian population, carbamazepine (18.2%) and phenytoin (13.4%)
were commonly implicated drugs [2].
Identification of candidate genes that predispose to anticonvul-
sant induced severe cutaneous reactions offers the possibility of
avoiding the drug in genetically susceptible individuals. HLA mol-
ecules are crucial for antigen presentation to T cell receptor. The
HLA genes are located at the major histocompatibility (MHC)
region on small arm of human chromosome 6p, spanning approx-
imately 200 genes. There are more than 10 highly polymorphic
HLA genes, including, HLA-A, HLA-B, HLA-C, HLA-DR, HLA-DQ
and HLA-DP loci. HLA-B is the most polymorphic gene in the
human genome [3].
Studies have suggested an association between HLA-B⁄
1502
and carbamazepine induced SJS in patients of Chinese/Asian eth-
nicity [4]. The data from the Indian population is scant. There are
no guidelines for screening for HLA-B⁄
1502 prior to prescribing
carbamazepine in India. There is urgent need for studies to deter-
mine the prevalence of SJS/TEN, and HLA B⁄
1502 in various ethnic
groups in Asia and its association with carbamazepine-induced
SJS-TEN in each of these ethnic groups. In view of the significant
morbidity and mortality in SJS-TEN, facilities should be developed
for screening of HLA B⁄
1502 before carbamazepine is prescribed in
the susceptible population. The aim was to explore the association
of HLA-B⁄
1502 and carbamazepine and phenytoin induced SJS/
TEN.
2. Materials and methods
The study design was case–control and hospital based. It was
conducted over a 2-year period from February 2012 to February
2014. Patients with a history of SJS or TEN secondary to carbamaz-
epine or phenytoin were recruited from the Neurology outpatient.
SJS was defined as skin detachment of 610% of body surface area.
TEN was defined as skin detachment of P30% [5]. The control
group comprised of patients who had received carbamazepine or
phenytoin for P6 months without any adverse cutaneous event.
http://dx.doi.org/10.1016/j.humimm.2014.09.022
0198-8859/Ó 2014 Published by Elsevier Inc. on behalf of American Society for Histocompatibility and Immunogenetics.
⇑ Corresponding author. Fax: +91 172 274401.
E-mail address: ritu_immunopath@yahoo.co.in (R. Aggarwal).
Human Immunology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
www.ashi-hla.org
journal homepage: www.elsevier.com/locate/humimm
Please cite this article in press as: Aggarwal R et al. HLA-B⁄
1502 is associated with carbamazepine induced Stevens–Johnson syndrome in North Indian
population. Hum Immunol (2014), http://dx.doi.org/10.1016/j.humimm.2014.09.022

2. One milliliter of blood was collected in EDTA from cases as well
as controls and was subjected to DNA extraction using a commer-
cially available kit (Qiagen, Hilden, Germany). The quantity of the
DNA was estimated by spectrometry and quality was established
by performing polymerase chain reaction (PCR) for beta actin, a
housekeeping gene. Subsequently, PCR with 48 sequence specific
primers for HLA-B antigen was performed. Cases positive for
HLA-B⁄
15 antigen were subjected to high resolution HLA-B⁄
15 typ-
ing using sequence specific primers. Commercially available kits
for low resolution DNA typing for HLA-B and high resolution
HLA-B⁄
15 (Invitrogen, Life Technologies, Carlsbad, CA, USA) were
utilized. The study was approved by the Institutes Ethics Commit-
tee. Written informed consent was obtained from each patient/
control.
Statistical analysis of the difference in the frequency of HLA-
B⁄
1502 among patients and controls was performed by Fisher’s
exact test (GraphPad Software, Inc., CA, USA). The reported p values
are two tailed. p values <0.05 are considered significant.
3. Results
Seventeen patients with a history of SJS/TEN secondary to car-
bamazepine (9) or phenytoin (8) were enrolled as cases. Fifty anti-
convulsant tolerant patients (carbamazepine-37; phenytoin-13)
formed the control group. The mean age of the patients and con-
trols was 33.9 ± 11.6 years (range: 15–50) and 28.1 ± 9.9 years
(range: 15–55), respectively. Among the SJS/TEN patients, 13 were
females and 4 males (M:F 1:3.2). Among the controls, M:F ratio
was 3:2. Majority of the cases were of SJS – 13 (76.4%), followed
by TEN – 3 (17.6%) and a single case of SJS/TEN overlap. Mucosal
lesions were observed in 8 (47%).
HLA-B⁄
1502 was observed in 2 of 9 (22.2%) carbamazepine-SJS/
TEN patients and none of the 37 carbamazepine tolerant controls
(p = 0.035). Both the patients with HLA-B⁄
1502 genotype were het-
erozygous. HLA-B⁄
1502 was not observed in any of the 8 phenytoin
induced SJS/TEN patients or the 13 phenytoin tolerant controls.
Other HLA-B genotypes observed in SJS/TEN patients included
HLA-B⁄
1505 (carbamazepine) and HLA-B⁄
1518 (phenytoin) in one
each. In tolerant controls, HLA-B⁄
1517 was observed in 4 (8%),
HLA-B⁄
1501 in 2 (4%) and HLA-B⁄
1510 in 1 (2%); none had a
HLA-B75 genotype. The sensitivity and specificity of HLA-B⁄
1502
for carbamazepine induced SJS/TEN was 22.2% and 100%,
respectively. The corresponding positive and negative predictive
value were 100% and 84.1%, respectively.
TEN and SJS are acute life threatening conditions. Epidermal
necrosis causes erosion of the mucous membrane, extensive
detachment of the epidermis and severe constitutional symptoms.
These conditions are capable of killing or severely disabling previ-
ously healthy people. Different anticonvulsant drugs have varying
potential to cause cutaneous adverse drug reactions. The common
drugs causing life threatening SJS/TEN differ from country to coun-
try. In Europe, carbamazepine is the most common causative drug
accounting for 8.2%, followed by phenobarbital (5.3%) and phenyt-
oin (5%) [6]. In Asia, particularly, Southeast Asian countries, car-
bamazepine accounts for an even higher share of SJS/TEN; 26% in
Taiwan, 35.7% in Malaysia and 27.7% in Singapore [7].
Etiology of 57 patients with TEN/SJS, treated over a period of
6 years has been previously reported from our centre [8]. Anticon-
vulsants were responsible for 44% of life threatening TEN/SJS. Phe-
nytoin and carbamazepine was the incriminating drug in 11 (19%)
cases, each [8]. In another retrospective study from South India,
etiology of 41 patients with TEN/SJS was evaluated [9]. Carbamaz-
epine and phenytoin were the incriminating drugs in 18 (32%) and
3 (5%) cases, respectively. Authors opined that the increased num-
ber of prescriptions of carbamazepine for the control of pain was
the plausible reason for the increased frequency of SJS/TEN due
to carbamazepine [9].
The mechanism by which drugs result in cutaneous adverse
reaction is ill understood. Immune reactions can be involved in
SJS/TEN; a re-challenge with the same drug typically results in
severe symptoms within 2–3 days. In addition, cytotoxic T cells
infiltrate the skin lesions of SJS/TEN. The blister fluid in the lesions
demonstrate a predominance of CD8+ phenotype [10]. The obser-
vation indicate that CD8+ T cell mediated cytotoxic response are
the major events in SJS/TEN [10].
HLA-B⁄
1502 was found in 22.2% patients with carbamazepine
induced SJS/TEN in our study as compared to none of the controls
(p = 0.035). The first drug-induced HLA-B⁄
1502 allele-associated
case from India was reported in 2009 [11]. Subsequently the lone
series was reported from the western state of Gujarat; HLA-
B⁄
1502 was identified in 6 of 8 (75%) patients with carbamaze-
pine-SJS/TEN [12]. Several more studies need to be conducted to
identify the frequency of HLA-B⁄
1502 in different regions of the
diverse population of India. The less strong association observed
in our study as compared to the one from Gujarat could possibly
Table 1
Selected studies of association of HLA-B⁄
1502 with anticonvulsant induced Stevens–Johnson syndrome and toxic epidermal necrolysis.
S.
No.
Country, year of
publication, reference
No. of patients Drug Association with HLA-B⁄
1502 Ethnicity
1 Taiwan, 2004 [4] SJS/TEN: 44;
tolerant
controls: 101
Controls:93
CBZ 44 (100%); tolerant controls: 3%, controls: 8.6% Han Chinese
2 Europe, 2006 [15] SJS/TEN: 12; CBZ No association in European population. 4 (100%) association
in those with Asian ancestry
Germany, France, Vietnam, China,
Cambodia and Reunion island
4 Thailand, 2008 [16] CBZ-SJS: 6
PHT-SJS: 4
tolerant
controls: 50
CBZ,
PHT
6 (100%): CBZ
4 (100%): PHT
8 (19%): CBZ-tolerant
8 (18%) PHT-tolerant
Thai population
5 Hong Kong, 2007 [17] CBZ-SCR: 4
PHT-SCR: 1
tolerant
controls: 48
CBZ,
PHT
4 (100%): CBZ-SCR
1 (100%): PHT-SCR
Han Chinese
6 India, 2009 [12] SJS: 8
controls: 10
CBZ 6 (75%): CBZ Controls: nil Western India
7 Japan, 2010 [18] SJS/TEN: 14 CBZ Nil Japanese
8 Thailand, 2010 [19] SJS/TEN: 42
tolerant
controls: 42
CBZ 37 (88%): CBZ
5 (12%): CBZ-tolerant
Thai population
SCR, severe cutaneous reaction; CBZ, carbamazepine; PHT, phenytoin; SJS, Stevens–Johnson syndrome; TEN, toxic epidermal necrolysis.
2 Rapid Communication / Human Immunology xxx (2014) xxx–xxx
Please cite this article in press as: Aggarwal R et al. HLA-B⁄
1502 is associated with carbamazepine induced Stevens–Johnson syndrome in North Indian
population. Hum Immunol (2014), http://dx.doi.org/10.1016/j.humimm.2014.09.022

3. be explained by the varied genetic ancestry. North Indians are con-
sidered to be genetically closer to Caucasians with a possible origin
in Eurasia, whereas the west central India which includes ethnic
population of Gujarat is more closely related to other Asian than
European groups [13,14]. Selected studies of association of HLA-
B⁄
1502 with anticonvulsant induced SJS/TEN are illustrated in
Table 1.
A pharmacogenetic study is more likely to yield a positive result
when conducted in a population with a high frequency of the
incriminated allele [20]. Association of up to 100% has been
reported from selected regions/ethnic populations, e.g., Han Chi-
nese and Thai population [4,16]. The strong association points
towards a direct functional involvement of HLA molecules in the
pathogenesis. Greater than 15% of the population is reported posi-
tive for HLA-B⁄
1502 in Hong Kong, Malaysia, Thailand and parts of
the Philippines, compared to about 10% in Taiwan and 4% in North
China [21]. South Asians, including Indians, appear to have inter-
mediate prevalence of HLA-B⁄
1502, averaging 2–4%. HLA-B⁄
1502
is present in <1% of the population in Korea and Japan [21]. HLA-
B⁄
1502 is largely absent in Caucasians, African-Americans, Hispan-
ics, and Native Americans [21].
Apart from HLA-B⁄
1502, other members of HLA-B75 serotype
have been implicated in carbamazepine-SJS/TEN. Kaniwa et al.
from Japan reported association of HLA-B⁄
1511 in 4 (29%) patients
of SJS/TEN, however did not detect HLA-B⁄
1502 [18]. HLA-B⁄
1511
belongs to the category of HLA-B75 serotype as does HLA-
B⁄
1502. The other members include HLA-B⁄
1508, HLA-B⁄
1505
and HLA-B⁄
1521. Mehta et al. from India observed HLA-B⁄
1508 in
1/8 carbamazepine-SJS/TEN patients and HLA-B⁄
1521/95 in 2/10
normal controls [12]. HLA-B⁄
1518 in Japanese and HLA-B⁄
1521 in
Thai population have been reported in carbamazepine-SJS/TEN as
well [19,22]. Wei et al. rationalized that similar amino acid
sequence homology may resemble structural features of HLA-
B⁄
1502 and thus may be able to trigger a similar cutaneous adverse
reaction to carbamazepine [23]. We did not detect any HLA-B75
serotypes, other than HLA-B⁄
1502 in selected patients with SJS/
TEN. Interestingly, recent studies have demonstrated an associa-
tion between HLA-A⁄
3101 and CBZ-induced adverse drug reactions
in Caucasian and Japanese populations [24].
The strong associations with HLA alleles support an important
role for HLA molecules in drug hypersensitivity, and it favors the
hapten concept [25]. However, 78% of patients with CBZ-induced
TEN/SJS lacked HLA-B⁄
1502 in our study. It is plausible that other
susceptibility genes may be located beyond the range of genotyp-
ing screening. It might be possible that the non-covalent direct
interaction of the drug or metabolite with matching T cell recep-
tors with MHC molecules triggers an immune response [25].
Unlike carbamazepine-SJS/TEN there was no association
between phenytoin-SJS/TEN and HLA-B⁄
1502 in our study. In a
study from Thailand, Locharernkul et al. observed HLA-B⁄
1502 in
4 (100%) patients with phenytoin-SJS and in 8 (18%) phenytoin tol-
erant controls (p = 0.005) [16]. The M:F ratio of patients with SJS/
TEN in our study is 1:3.2. The skewed female majority is likely a
random finding. The M:F ratio of patients with carbamazepine-
induced SJS/TEN in the previous study from India was 1:1 [12].
The ratio was 2:1 in a European study that comprised patients of
varied ethnicity [15].
HLA-B⁄
1502 is a risk factor for carbamazepine induced SJS/TEN
in North Indian population. Given the serious and life threatening
consequences of developing SJS/TEN and the availability of alterna-
tive drugs, HLA-B⁄
1502 testing should be performed prior to initi-
ating carbamazepine in India. Physicians in India should be made
aware; facilities for testing HLA-B⁄
1502 should to be easily
accessible and economical.
Acknowledgment
The study received funding from the Post Graduate Institute of
Medical Education and Research, Chandigarh.
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Rapid Communication / Human Immunology xxx (2014) xxx–xxx 3
Please cite this article in press as: Aggarwal R et al. HLA-B⁄
1502 is associated with carbamazepine induced Stevens–Johnson syndrome in North Indian
population. Hum Immunol (2014), http://dx.doi.org/10.1016/j.humimm.2014.09.022