Page 161 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-76 Rashes

URTICARIA

Urticaria is a commonly encountered skin condition
with a multitude of causes. There are primary and sec-
ondary forms of urticaria. Most secondary causes are
acute in nature and can be explained by an underlying
disease state, medication, or food. Urticaria can be a
manifestation of many disease states, such as Muckle-
Wells syndrome. Urticaria can also be a secondary
sequela of an underlying malignancy, acute or chronic
infection, genetic disease, and rheumatologic disease. It
can also be seen as an acute reaction in a patient with Urticaria: Pink edematous
anaphylaxis. plaques with follicular
Primary urticaria can be divided into subsets of accentuation caused by the
disease. The most common type is chronic idiopathic dermal edema.
urticaria. Other forms of primary urticaria include the
physical urticarias. There are many forms of physical
urticaria, and the astute clinician can perform provoca-
tive testing to determine the type. There is no known
cure for urticaria, but most cases of primary urticaria
spontaneously resolve within 2 to 3 years.
Clinical Findings: Primary idiopathic urticaria is one
of the most frequently encountered forms of urticaria.
If no underlying cause is found and the urticaria lasts
longer than 6 weeks, it is given the designation chronic
idiopathic urticaria. This form of urticaria comes and
goes at will with no provocative or remitting factors.
Lesions appear as evanescent, pink to red, edematous
plaques or hives. They can occur anywhere on the body
and can cause much distress to the patient because of
their appearance and because of the severe pruritus.
Patients are particularly distressed when the hives affect Annular and serpiginous
the face and eyelids, causing periorbital and periocular urticaria: This is a less
swelling. Patients with chronic urticaria usually undergo commonly seen variant of
a battery of laboratory and allergy tests. A complete urticaria.
blood count, metabolic panel, chest radiograph, and
measurements of thyroid-stimulating hormone and
antithyroid should be performed, as well as testing for
various infectious diseases if the medical history war-
rants. Testing for hepatitis B, hepatitis C, and HIV
infection can be done in the appropriate clinical setting.
Patients with a travel history often undergo stool exam-
inations for ova and parasites. A full physical examina-
tion is warranted, together with age-appropriate cancer
screening. Most patients with chronic urticaria have no
appreciable cause for their hives and are diagnosed as
having chronic idiopathic urticaria.
The physical urticarias are a group of conditions that
cause hives; they represent a unique form of chronic
idiopathic urticaria in that there is a precipitating factor.
There are many types of physical urticaria, including Solar Urticaria: Note the areas affected are
aquagenic and cholinergic forms and cold-, pressure-, those only exposed to the sun in this sleeve-
solar-, and vibratory-induced urticaria. These forms are less shirt wearing man. Cholinergic urticaria: This
diagnosed based on the results of provocative testing. form of urticaria can be
The clinical history often leads to the diagnosis and the induced by increasing the body
appropriate testing regimen. As an example, a patient temperature through exercise
may develop hives only under tight-fitting socks. This or submersion in a warm bath.
is typical for pressure-induced urticaria. If the patient
develops hives on appropriate provocative testing, the
diagnosis is made.
Pathogenesis: The pathogenesis of urticaria is poorly Many medications have been shown to cause mast Treatment: Treatment of chronic idiopathic urticaria
understood. Mast cells play a critical role. A stimulus cell degranulation without an IgE-mediated pathway. is based on symptom relief. Antihistamines are the first-
causes mast cells to release histamine, which acts on the The most common of these are the opiates and anes- line therapy and can be used in combination. The lack
local vasculature to increase vascular permeability. The thetic agents. Chemical transmitters other than hista- of response can be frustrating for both patient and phy-
increased permeability causes localized swelling. Some mine also play a role in urticaria; they include the sician. Physical urticarias are treated in the same
forms of urticaria, such as those seen in anaphylaxis, are leukotrienes, serotonin, and various kinins. manner, with emphasis on avoidance. Patients who can
caused by a type I hypersensitivity reaction. Other Histology: The histological findings in urticaria are avoid exposure to the physical stimulus responsible for
forms of secondary urticaria may be caused by specific bland. The specimen typically shows a superficial peri- the urticaria have been shown to have a better clinical
immunoglobulin E (IgE) antibodies that interact with vascular lymphocytic infiltrate with some dermal outcome.
mast cells. edema. The epidermis is normal.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 147