Type IV Hypersensitivity Flashcards
What type of hypersensitivity is Type IV hypersensitivity?
Cell-mediated
Are antibodies involved in type IV hypersensitivity?
No
Types of Type IV hypersensitivity
Delayed-type, cytotoxic cell-mediated
What happens in delayed hypersensitivity?
Upon initial exposure to the antigen, the person’s body formed B memory cells with sensitized lymphocytes and facilitated by T-helper cells.
Cell death results from cytotoxic T-lymphocytes, associated cytokines, and recruitment of macrophages
Chronic and acute diseases manifested by cell-mediated hypersensitivity
TB, leprosy, schistosomiasis, contact dermatitis, eczema, SJS, TEN, SJS/TEN, AGEP
What kind of hypersensitivity is contact dermatitis? (Specific subset of Type IV)
IVa, IVc
Causes of contact dermatitis
Cosmetics, drugs, clothes dye, food, rubber, latex, poison ivy/mango leaves
Signs/Sx of contact dermatitis
Burning or stinging with erythema, swelling, peeling, blisters with oozing and crusting, possibly severe itching
Time of onset of contact dermatitis symptoms
Within a few hours of exposure
Contact dermatitis treatment
Topical steroids, antihistamines, topical immunomodulators (topical calcineurin inhibitors), systemic steroids, cold compresses, calamine lotion, oatmeal baths, mild soaps, non-irritating moisturizers, non-scented detergents, avoid known triggers, wash skin after exposure
What kind of hypersensitivity is SJS, TEN, SJS/TEN? (Specific subtype of Type IV)
Type IVc
Body distribution of SJS
<10% of BSA
Body distribution of TEN
> 30% of BSA
Body distribution of SJS/TEN
15-30% of BSA
Clinical presentation of SJS, TEN, SJS/TEN
Macules that rapidly spread and coalesce, leading to epidermal blistering, necrosis, and sloughing
Symptoms of SJS, TEN, SJS/TEN
Sore throat, fever, fatigue, burning eyes for 1-3 days; tingling/burning of skin early on, ulcers and other lesions appear in mucous membranes, conjunctivitis, rash of lesions on the face, arms, trunk, legs, soles -> blisters develop and erosion of confluent macules
Populations at risk of SJS, TEN, SJS/TEN
Bone marrow transplant patients, Pneumocystis jirovecii-infected HIV patients, patients with SLE, patients with chronic rheumatologic diseases, middle-aged and older women
Pharmacologic causes of SJS, TEN, SJS/TEN
Sulfa drugs, ABX (aminopenicillins like ampicillin, amoxicillin, fluoroquinolones, cephalosporins), antiepileptics, piroxicam, allopurinol
Non-pharmacologic causes of SJS, TEN, SJS/TEN
Infection, viral, vaccination, graft vs. host disease
Treatment of SJS, TEN, SJS/TEN
Stop offending agent, wound care, eye care, pain management, fluid, electrolyte, nutrition management, cyclosporine and etanercept
What kind of hypersensitivity is AGEP? (Specific subset)
Type IVd
Clinical presentation of AGEP
Rapid appearance of hundreds to thousands of small, non-follicular subepidermal and intradermal sterile pustules with a background of erythema
Onset of AGEP
Up to 3 weeks after drug exposure
Drugs that cause AGEP
Aminopenicillins, sulfonamides, quinolones, hydroxychloroquine, terbinafine, diltiazem
AGEP Treatment
Stop offending agent, fluid, electrolyte, nutrition management, topical corticosteroids, PO antihistamines, analgesics
What kind of type IV hypersensitivity is a TB test?
IVa
TB test looks to see…
…whether or not a patient has had prior exposure to TB (having the virus or getting the live attenuated vaccine for it)
TB test
Intradermal injection of TST in the upper arm, observe 48-72 hours later.
A positive TB test is…
…a wheal and flare response of >5mm
Anergy definition
Absence of a cell-mediated immune response
Anergy is what type of hypersensitivity reaction?
Type IV
A false negative to a TB test may result in these patients with anergy…
Elderly, severely debilitated, disseminated TB, HIV, patients taking immunosuppressive treatment, glucocorticoid therapy, patients who had a recent viral infection
What happens if anergy is suspected?
Use control skin tests of candida or mumps; if one of the controls is positive but the TB one is still negative then they didn’t have prior exposure to TB
