0071643192.pdf

HEMATOLOGY, ONCOLOGY, ALLERGY,

AND IMMUNOLOGY

Anaphylaxis and Anaphylactoid Reactions

Anaphylaxisis anIgE-mediated systemic, immediate hypersensitivity reaction

to a specific antigen. IgE causes release of histamine, serotonin, leukotrienes,

and prostaglandins from basophils and mast cells. Common causes are listed

in Table 9.13.

Anaphylactoid reactionsresult from direct release(no IgE) of mediators

listed above. Common causes are listed in Table 9.13.

SYMPTOMS/EXAM

■ Urticaria, pruritis, angioedema, wheezing, stridor, hypotension, abdominal

cramps, nausea/vomiting, diarrhea

■ Hypotension during anaphylaxis is a form of distributive shock (like sepsis) in

which systemic vascular resistance is decreased. The skin should be warm.

DIAGNOSIS

■ Clinical diagnosis: Angioedema, cutaneous manifestations, history of incit-

ing antigen, respiratory, or cardiovascular collapse

TABLE 9.12. Hypersensitivity Reaction

TYPE OFREACTION MECHANISM EXAMPLE

Type I: Anaphylactic IgE-mediated degranulation of Anaphylaxis

mast cells with release of Urticaria

mediators Angioedema

Type II: Cytotoxic IgG or IgM antibodies react with Autoimmune hemolytic

cell antigens with resultant anemia

complement activation Goodpasture syndrome

Type III: Immune complex Immune complex deposition Serum sickness

and subsequent complement SLE

activation RA

Type IV: Cell-mediated Activated T cells against cell Contact dermatitis

surface bound antigens

TABLE 9.13. Common Causes of Anaphylaxis and Anaphylactoid Reactions

ANAPHYLAXIS ANAPHYLACTOIDREACTION

Medications (any prescription or OTC medications) Radiographic IV dye

Food (shellfish, nuts, milk, eggs) Blood products

Insect stings (hymenoptera) Opioids (morphine)

Latex Scombroid

Most serious reactions may

usually occur within minutes

of exposure. Some patients,

however, may experience a

recurrence of symptoms in

4—8 hours.

Penicillins and cephalosporins

cause>100 anaphylaxis

deaths each year in the United

States and are among the

most common causes of fatal

anaphylaxis.