-IBIS-1.5.0-
tx
cutaneous system
urticaria
diagnoses
definition and etiology
definition:
localized wheals and erythema in the superficial portion of the dermis that may join to form giant lesions; also called "hives"; closely related to angioedema
etiology:
Urticarial reactions are relatively common, with an estimation that up to 15-20% of the population has had at least one episode. Although it is seen in all ages, it seems to be more prevalent among young adults (post-adolescence until 30 years old). The reaction involves the release of inflammatory mediators from either mast cells or basophilic leukocytes causing IgE responses. The causes of urticaria are many and, in 80% of the cases, are not determined, which explains why so many patients become chronic. Some initiating factors include:
allergic urticaria: inhalants (pollens), injectants (drugs, blood), ingestants (foods), infections, contactants (animal dander, cosmetics), drugs (oral, esp. penicillin, salicylates), toxins (jellyfish, fleas)
physical urticaria: heat or sun, cold, light, pressure (bracelets, clothes), dermographic, vibration (lawn mower), exercise
secondary urticaria: infections, collagen vascular diseases, neoplasia, psychogenic, other (hypothyroidism, polycythemia vera)
The most common causes of chronic urticaria are drug reactions, stress, food sensitivities and fungal infections
signs and symptoms
signs and symptoms:
pruritus: usually the first symptom
wheals: 1-5 mm to large circinate patterns that cover an entire extremity or the trunk (50% of patients develop plaques); lesions are white or red with a pale center and serpiginous borders
lesions characteristically come and go from area to area
in extreme acutes, tongue and glottal involvement may present, along with peripheral vascular compromise; this may be a medical emergency
lab findings:
in acute urticaria, there are usually no remarkable lab values; eosinophilia is (-)
in chronic urticaria, lab work should include CBC, ESR, UA and dental and sinus examinations to rule out a hidden pathology
allergy testing
course and prognosis
Acute urticaria lasts from 1-7 days, and treatment is not usually needed except for palliation. The inciting agent must be dealt with, whether food, external agent or emotion. In rare, severe cases 1:1000 epinephrine may be required. In chronic urticaria (> three weeks) 50% of patients experience spontaneous remission within two years, even though in the majority of cases the cause is never identified.
differential diagnosis
angioedema: similar eruptions that involve deeper layers of skin including the subcutaneous tissues
infectious mononucleosis
SLE
erythema multiforme
bite reactions
footnotes