3. How drugs are recognized by the
immune system?
Pathomechanism
4. Hapten and prohapten concepts and noncovalent drug
presentation to T cells
Med Clin N Am 94 (2010) 645–664
5. Acylation of lysine residues in serum or cell surface proteins results in penicilloyl or major
antigenic determinant. From its isomer penicillanic acid, other covalent linkages to
macromolecules can occur to produce a variety of less common and/or less dominant ‘minor’
epitopes.
Middleton’s allergy. Seventh edition.
6. Sulfonamide metabolism and haptenation. Sulfonamides are metabolized by N4-oxidation by
cytochrome P450 enzymes or by N4-acetylation. N-acetyl sulfonamides and glutathionyl
(GSH) sulfonamides are then excreted. Free sulfonamides, N-acetyl sulfonamides, and GSH
sulfonamides have the potential to act as univalent inhibitors of antibody-mediated reactions.
Carrier haptenation can occur after N-oxidation if the capacity for GSH conjugation is
exceeded
Middleton’s allergy. Seventh edition.
7. The p–i concept of T lymphocyte activation. The drug happens to fit into some TCR (1) with sufficient affinity
to cause a signal. This drug-TCR interaction is supplemented by MHC interaction (2). The T cells react and
proliferate. No metabolism of drugs required. The reactive T cell is probably preactivated and has an
additional peptide specificity.
Middleton’s allergy. Seventh edition.
8. Evidence for p-i mechanism :
◦ Aldehyde-fixed APC are still able to activate specific TCC if
incubated together with drug
◦ drug binding to proteins more labile than covalent interactions
of haptens and can be washed away
◦ Calcium influx in TCC happens within seconds ; before drug
uptake, metabolism, and processing can occur
clinical features of p-i concept are as
follows:
◦ Positive skin test reactions to inert drugs, although no
cutaneous metabolism of this peculiar drug is known
◦ Immune reactivity at first encounter, without time of sensitization
◦ Higher risk in viral infections, to lower threshold for T cell
reactivity
◦ Fulminant course (as with superantigen stimulations)
◦ reflects abnormal T-cell stimulation with massive/fatal self-
destruction as seen in SJS/TEN and DRESS/DiHS
Med Clin N Am 94 (2010) 645–664
12. Characteristic chronology of drug-induced eruptions.
separation at 1 hour into immediate or nonimmediate reactions not
sufficiently reflect large overlap between pathophysiologically
determined immediate- and delayed-type clinical manifestations
Med Clin N Am 94 (2010) 711–725
13. Revised Gell and Coombs classification of drug
reactions
Med Clin N Am 94 (2010) 645–664
14. T cell orchestrated hypersensitivity reactions
(Gell and Coomb's types IVa–d)
Middleton’s allergy. Seventh edition.
16. Maculopapular or morbilliform exanthema
most common
initially with erythematous
macules and infiltrated papules,
affecting particularly trunk and
proximal ext.
(Classic) appear after 7 to 10
days
DDx : classic infectious
exanthems eg. measles and
rubella
In more severe reactions,
elevated eosinophil counts (~ 50%
of pts.)
Common elicitors : ATB
(aminopenicillins and quinolones),
antiepileptic drugs, RCM
First signs eg. discrete erythema
may even appear after a few
Med Clin N Am 94 (2010) 665–679
hours
17. Systemic danger signs for severe delayed-type
reactions
Fever
Malaise
Prolonged clinical symptoms after
discontinuation of the causative drug
Lymphadenopathy
Eosinophilia >1.5* 109 cells /liter
Liver involvement
Med Clin N Am 94 (2010) 665–679
19. Central facial erythematous swelling in
DRESS syndrome (left), SJS (middle), and
TEN (right) (diffuse erythematous swelling)
Med Clin N Am 94 (2010) 681–689
20. Atypical target lesions( SJS/TEN )
Typical target lesions
< 3 cm in diameter with a only 2 zones, are mostly
regular round shape, flat, and irregular shape
well-defined border, and darker color and
2 concentric rings around sometimes central
a central disk blister
Med Clin N Am 94 (2010) 681–689
21. Positive Nikolsky sign in edematous,
erythematous skin indicating necrolytic
detachment of epidermis in SJS/TEN
Med Clin N Am 94 (2010) 681–689
22. Severe mucositis in a patient with TEN,
manifesting >1 day before epidermolysis of
skin was detectable
Med Clin N Am 94 (2010) 681–689
23. Cutaneous danger signs for severe delayed-
type reactions
Involvement of large body surfaces or
erythroderma
Painful skin, skin tender to touch
Hemorrhagic necrotizing lesions
Purpura
Med Clin N Am 94 (2010) 681–689
24. Clinical symptoms and laboratory
findings of DIHS/DRESS
Med Clin N Am 94 (2010) 743–759
25. Face swelling in early manifestation of
DRESS syndrome
occurs in 1 in 1,000 -
10,000 exposures to
antiepileptic drugs
2 -12 weeks after
initiation of specific
drug therapy
Mortality ~ 10%
anticonvulsants,
dapsone, allopurinol,
and minocycline
DDx : viral infection
( EBV, CMV ),
autoimmune
Med Clin N Am 94 (2010) 691–710
26. Diagnostic criteria for DRESS
MP rash developing > 3 weeks after starting with
drugs
Prolonged clinical symptoms after discontinuation of
causative drug
Leukocyte abnormalities (at least 1 present):
◦ Leukocytosis (>11 * 109 cells / liter)
◦ Atypical lymphocytosis (>5%)
◦ Eosinophilia (>1.5 * 109 cells / liter)
Lymphadenopathy
Fever (>38ºC)
Liver abn. (ALT >100 U/L) or other organ
involvement
HHV 6 reactivation (during 2nd to 3rd week after start
Med Clin N Am 94 (2010) 665–679
of symptoms)
27. Time interval between onset and visceral
involvements during course of DIHS/DRESS
Med Clin N Am 94 (2010) 743–759
28. Visceral organ involvements in acute stage
Hepatitis
◦ most common (~70%)
◦ If icteric, poorer prognosis
◦ Coagulopathy in severe case
◦ Steroid benefit in fulminant hepatitis
◦ In Europe, 1 mg/kg/d of prednisolone recommended, if ALT >500 IU, Tapering
according to clinical course, too early CS reduction tends to transient
exacerbations
◦ NAC ( case report, 24g/d over 3 d )
Nephritis
◦ ~11%
◦ kidney biopsy : AIN with lymphocytic infiltrate and ATN ( case SSZ )
Hemophagocytic syndrome (HPS)
◦ Rare
◦ triggered by viral infection, malignant tumors, or autoimmune diseases
Myocarditis
◦ Rare
Med Clin N Am 94 (2010) 743–759
31. SJS and TEN
incidence of TEN 1.89 cases per million
per year
Genetic susceptibility
◦ HLA-B*1502, SJS, carbamazepine in Han
Chinese ( OR =2504 ), not in Europe
◦ HLA-B*5801, SJS and TEN , allopurinol
(OR= 80) independent of ethnic background
differential diagnoses
◦ EM major
◦ Autoimmune bullous disorder: Linear IgA
bullous dermatosis, BP, paraneoplastic
pemphigus
◦ SSSS
Am J Clin Dermatol 2003.
32. Clinical features that distinguish
SJS, SJS-TEN overlap, and TEN
Med Clin N Am 94 (2010) 727–742
33. Drugs with high risk of inducing SJS/TEN
Antibiotics
◦ TMP/SMX
◦ Aminopenicillin
◦ Cephalosporin
◦ Quinolone
Anticonvulsant
◦ Carbamazepine
◦ Phenytoin
◦ Phenobarbital
Nevirapine
Oxicam-NSAID
Allopurinol(most common in Europe and Israel
) Med Clin N Am 94 (2010) 727–742
34. Management and Therapy
Prompt withdrawal of culprit drugs and
supportive care
Drug therapy , specific therapy does not
exist
High-dose IVIg
◦ 8 /11 studies may be benefit of IVIG used (>2
g/kg over 3 to 4 days ) on mortality ( TEN )
CsA : insufficient to draw conclusions
Systemic steroid : remains controversial
prevention of ocular complications
Med Clin N Am 94 (2010) 727–742
35. SCORTEN severity-of-illness score
SCORTEN Parameter Individual SCORTEN (Sum Predicted
Score of Individual Mortality
Scores) (%)
Age>40 years Yes = 1, No = 0 0–1 3.2
malignancy Yes = 1, No = 0 2 12.1
Tachycardia (>120/min) Yes = 1, No = 0 3 35.8
Initial surface of Yes = 1, No = 0 4 58.3
Epidermal detachment >10%
Serum urea >10 mmol/L Yes = 1, No = 0 5 90
( 28 mg/dl )
Serum glucose >14 mmol/L Yes = 1, No = 0
(252 mg/dl )
Bicarbonate <20 mmol/L Yes = 1, No = 0
Med Clin N Am 94 (2010) 727–742
Average mortality : SJS 1- 5%, and TEN 25- 35%
36. Acute generalized exanthematous
pustulosis
5 cases per million
annually
females > males
mean age 56 years
Treatment
◦ Exclude infectious dis.
◦ intermediate to high
doses of systemic
corticosteroids over
several days
◦ local corticosteroids of
high potency applied
for 5 - 10 days
Med Clin N Am 94 (2010) 727–742
37. Differential diagnoses of
AGEP
Generalized pustular psoriasis
Subcorneal pustulosis
Subcorneal IgA dermatosis
Infectious folliculitis
Viral exanthema with secondary
pustulation
Sweet syndrome(neutrophilic dermatosis )
Med Clin N Am 94 (2010) 727–742
38. Drugs with high risk for induction of
AGEP
Ampicillin/amoxicillin
Pristinamycin
Quinolone
Anti-infective sulfonamides
Terbinafine
Hydroxychloroquine
Diltiazem
Med Clin N Am 94 (2010) 727–742
42. Tests for detection of drug-specific T cells in
patients with delayed-type drug
hypersensitivity
Immunol Allergy Clin N Am 29 (2009) 537–554
43. Guidelines in drug skin testing
performed 6 weeks to 6 months after
complete healing of CADR
at least 1 month after discontinuation
of systemic corticosteroid or
immunosuppressive therapy
not to test during pregnancy
Contact Dermatitis, 2001, 45, 321–328
44. Drug Patch Testing
performed on upper back using Finn Chambers
read at 20 min, D2 and D4 ,D7 (if negative on D4)
In FDE, should be performed both on normal skin
and on residual pigmented site of FDE
with commercialized drug
◦ Incorporated at 30% in pet. and aq.
◦ made for only 1 patient and kept no > 1 D
with pure substances
◦ diluted at 10% in pet.& aq. or alcohol (alc.).
aciclovir, carbamazepine or pseudoephedrine
◦ first diluted at 0.1% and 1,10% ( in severe CADR)
Contact Dermatitis, 2001, 45, 321–328
45. Drug Patch Testing
value in generalized eczema, systemic
contact dermatitis, baboon syndrome, MP
rash , AGEP , lichenoid rash and fixed
drug eruption
less value in SJS, TEN, pruritus or
vasculitis
most frequent reports of positive patch
tests
◦ Betalactam esp. amoxicillin, Cotrimoxazole
◦ corticosteroids , heparin derivatives ,2001, 45, 321–328
Contact Dermatitis,
47. Drug Patch Testing
Negative results :
◦ drug metabolite not formed in skin
◦ no immune mechanism
◦ No concomitant factors eg. Viral infection
Best vehicle not yet been determined
◦ steroid hormone (in alcohol)
◦ Corticosteroid ( in water& alcohol)
◦ Ganciclovir ( in water )
Positive results vary (10-60%)
Contact Dermatitis, 2001, 45, 321–328
48. Intradermal Tests (IDT)
Contraindicated in SJS, TEN or LCV
diluted sequentially (10-4, 10-3, 10-2 and 10-1) in
phenolated saline or in 0.9% saline
performed on extensor surface of arm, with
small volume (0.04 ml) produces weal (4-6
mm)
Readings performed at 30 min, 6 h and 1 D (
1 week, if result are negative )
risk of eliciting relapse of initial CADR ( 3
minor incidents/30)
Contact Dermatitis, 2001, 45, 321–328
49. Intradermal test results positive for Patch test results positive for AX
AX and AM and AM
Nonimmediate skin test results
Med Clin N Am 94 (2010) 805–820
50. Drugs Patch test Intradermal test
Aminopenicillins 10% in Pet. 20-25 mg/ml
Cephalosporins 10% in Pet. 1/10 of full strength
Pristinamycin 10% in Pet.
Quinolone 30% in Pet. Or water 1/100 of full strength
Co-trimoxazole 10% in Pet. 1/100 of full strength
Minocycline 10% in Pet.
Carbamazepine 1%,10% in Pet.
NSAIDs (oxicams) 1%,10% in Pet.
51. Lymphocyte Transformation
Test
most widely used test
principle : simple proliferation test with Ag
useful in MPE, pustular exanthema, bullous
exanthema and DRESS
cultured in presence of suspected drug for 6
days
measured by incorporation of 3H-thymidine
during DNA synthesis
stimulation index (SI) >2 ( 3 for betalactam )
not necessarily associated with clinical
severity
Sensitivity 60- 70% (depends on drug tested,
Immunol Allergy Clin N Am 29 (2009) 537–554
> skin test )
52. Lymphocyte Transformation
Test
Specificity ~ 85%
Perform in 1-6 mo. After event ( bullous
dis., positive in first week of dis.)
False positive :vancomycin, possibly
paracetamol, and RCM
False negative :abacavir
disadvantages:
◦ requires sterile cell cultures
◦ takes a long time and cumbersome
◦ depends on quality of culture medium
◦ involves radioactivity, and expensive
equipment
Immunol Allergy Clin N Am 29 (2009) 537–554
53. CD69 UP-REGULATION
CD69 : membrane type II C-type lectin,
transiently expressed on activated
lymphocytes
up-regulated in T cells from patients who
had drug-induced MPE, erythema
multiforme, SJS, and DRESS when
assessed by flow cytometry
comparable to LTT
Advantage : not require radioactive
substances and less time-consuming
Disadvantage : flow cytometry-based
test, difficult to standardize
Immunol Allergy Clin N Am 29 (2009) 537–554
55. Measurement Of Drug-induced Cytokine
Production From Ex Vivo PBMC
measurement of IL-2, IL-5, IL-13, and IFN-γ
cytokines might be promising tool for detecting
drug sensitization in delayed-type reactions
ELISA or ELISPOT assay, or multiplexed bead-
based flow cytometric assays, mRNA by RT-
PCR
IFN-γ ELISPOT assay exhibited high sensitivity
and specificity since specific T cells were
detected in 20/22 ( 91%) of amox-DTH patients
only 1/26 nonDTH allergic patient had
unexpected but weak reactivity to unrelated
control antibiotic
Immunol Allergy Clin N Am 29 (2009) 537–554
Allergy 2009: 64: 534–542
56. ELISA ELISPOT
Immunol Allergy Clin N Am 29 (2009) 537–554
57. Cytotoxicity: Granzyme B Enzyme
Immunospot Assay
gives results 48 to 72 hours after stimulation
and not involve radioactivity
Once cytotoxic T cells get activated, lytic
granules reach plasma membrane,
granzymes and perforin released into
immunologic synapses, and cumulative
exposure of granular membrane proteins
(CD107a) can be measured on surface of
responding cytotoxic cells, providing positive
marker for degranulation
seems to be most sensitive and robust
method to detect cytotoxic cells in peripheral
blood of drug-allergic patients
Immunol Allergy Clin N Am 29 (2009) 537–554
59. When Should Diagnostic Tests Be
Performed?
recommend performing LTT within 1 week
after onset of skin rashes in MP eruptions
and SJS or TEN and > 5 to 8 weeks after
event in DRESS
some patients lose reactivity within 1 to 3
years after reaction
many groups carry out tests after of 3 weeks-
6 months after acute event
In vitro tests offer advantage of safety,
simultaneous assessment of T-cell responses
to multiple drugs, lack of risk for
resensitization, and insight into
pathomechanism
Immunol Allergy Clin N Am 29 (2009) 537–554
60. Conclusion
Delayed type drug hypersensitivity
classified by pathomechanism (type IVa-
d)
MP rash : most common
SJS/TEN : most severe, treatment is
supportive care ( may be try IVIg )
Skin test ( patch test, ID test ): low
sensitivity
In vitro test : LTT ( gold standard ), other
test remained study
rigid separation between immediate and nonimmediate reactions at 1 hour based on the chronology only may be problematic, because there is a considerable overlap of a period of approximately 2 to 6 hours between the reaction period of urticarial and exanthematous eruptions (see Fig. 2, Table 1). The terms immediate and delayed are also commonly used to depict the pathophysiology (ie, type I [IgE mediated]and type IV [T cell mediated]). This is most important with regard to the selection of appropriate diagnostic tests
Type IVa reactionscorrespond to Th1 reactions with high IFNg/TNFa secretion, and involve monocyte/macrophageactivation. CD8 cell recruitment (type IVc reaction) often occurs. Type IVb reactionscorrespond to eosinophilic inflammation and to a Th2 response with high IL-4/IL-5/IL-13secretion; they are often associated with an IgE-mediated type I reaction. Type IVc reactions:the cytotoxic reactions (by CD4 and CD8 cells) rely on cytotoxic T cells as effector cells (type IVc). They seem to occur in all drug-related delayed hypersensitivity reactions. Type IVd reactions correspond to a T-cell–dependent, sterile neutrophilic inflammatory reaction. It is distinct from the rapid influx of PMN in bacterial infections. It seems to be related to high CXCL-8/GM-CSF production by T cells
Erosive stomatitis; mucositis, especially if affecting more than one mucosa
typical dermoepidermal detachment and necrosis beneath the stratum corneum in SJS/TEN
Provocation test not well standardized in delayed reactions regarding dose, durationof symptoms, and definition of positivity, and are therefore difficult to perform
International Contact Dermatitis Research GroupIrritant reaction Controls show similar response or there was an excited skin responseDoubtful reaction Negative test result. Repeat readings at 3, 4, and 7 days after patch removed. If ACD still suspected, recheck technique or do ROAT1+Light erythema, nonvesicular Equivocal test result. Could either be negative or indicative of waning prior sensitization. False-positive test result or excited skin syndrome must be ruled out by test in control subject. Repeat steps in 3.2+ Edema, erythema, discrete vesicles Positive test result. Indicative of prior or current sensitization. Should correlate with history and physical findings. False-positive test result or excited skin syndrome must be ruled out by test in control subject3+ Coalescing vesiculobullous papules Strongly positive result.
(0.5% phenol in 0.9% saline)
large prospective study is required to evaluate this test and to determine sensitivity and specificity in drug hypersensitivity diagnosisThis prospective study is currently being performed by the authors’ drug allergy research group in Bern
necessary to evaluate anaccurate cutoff for positivity and the exact sensitivity and specificity of these assays