Internal Medicine

0521779407-21 CUNY1086/Karliner 0 521 77940 7 June 7, 2007 18:59

1500 Urticaria (Rheumatology)

■Laboratory vortex to vibrate forearm for 1 minute; prominent

swelling of extremity: vibrating angioedema

Chronic Urticaria

■Thyroid function tests (abnormal in 19%)

■Antibody to thyroglobulin (8% positive), microsomal antigens (5%

positive); antibodies to both in 14%

■ANA, especially in young women

■Autologous skin test w/ pnt serum is positive in about 35% & indicates

the presence of antibody to the IgE receptor & in 5% anti-IgE. It is

diagnostic of chronic autoimmune urticaria.

■Research assay – histamine release upon incubation of pt serum w/

basophils indicates an autoimmune cause in 45%; the remainder

have chronic idiopathic urticaria

■Skin biopsy if vasculitis suspected (eg, hives >36 hrs, increased ESR,

arthralgias & myalgias, petechiae or purpura w/ hives); angioedema

alone – recurrent

■Measure plasma C4 & C1 inhibitor (C1 INH) levels

➣If normal: idiopathic, the most common form of angioedema

➣If subnormal, consider hereditary angioedema or acquired C1

INH deficiency assoc w/ lymphoma, cryoglobulinemia, SLE, car-

cinoma or antibody to C1 INH

differential diagnosis

■Acute urticaria: food allergy, drug reactions, prodrome of hepatitis

B, infectious mononucleosis, transfusion reaction

■Chronic urticaria and/or angioedema: cutaneous vasculitis (1%)

management

What to Do First

■Note size, shape, distribution of any hives

■Test for dermatographism

■Check for angioedema: swelling of lips, tongue, pharynx, face,

extremities, penis, scrotum

■Emergency: epinephrine 1:1,000 subcutaneously, diphenhydramine

IV; tracheotomy for laryngeal edema

specific therapy

Acute Hives or Swelling

■If mild: nonsedating antihistamines (cetirizine, fexofenadine, lora-

tidine)

■Moderate: diphenhydramine, hydroxyzine