Hypersensitivity syndromes

The hypersensitivity syndromes are a group of diseases in which the cutaneous vasculature is altered through immunologic or nonimmunologic mechanisms. These reactions range in severity from mild to life-threatening and can be triggered by drugs, infectious agents, foods, or environmental allergens. Although their causes may vary, the morphologic appearance of these entities may be similar making a clinical diagnosis a challenge.

Acute and chronic urticaria. Challenges and considerations for primary care physicians

Urticaria and angioedema are common dermatologic problems seen by primary care physicians. A carefully taken history, physical examination, specific tests, and skin biopsy often provide useful diagnostic information. In patients with chronic urticaria, urticarial vasculitis and diseases that mimic urticaria need to be ruled out. A variety of treatment options are available for patients with urticaria and urticarial vasculitis. Pharmacologic therapy is useful when the specific cause is undetermined. When a trigger has been identified, the patient must avoid exposure to it. Patient education is an important component of management and should include instructions on crisis management, particularly for patients who have angioedema or a tendency for anaphylaxis.

Low molecular weight C1q-precipitins in hypocomplementemic vasculitis-urticaria syndrome: partial purification and characterization as immunoglobulin

A lupus-like syndrome involving chronic urticaria with cutaneous vasculitis, systemic symptoms, hypocomplementemia with preferential depletion of C1q, and low m.w. (7S) C1q-precipitins has recently been defined. The C1q-precipitin activity (C1q-p) seems to represent a diagnostic marker of the disease, but its chemical nature is not yet clear. We have partially purified and characterized C1q-p from the serum of two patients with this syndrome and compared its activity with the C1q-precipitating activity of aggregated human gamma-globulin (AHGG) anti-C1q antibodies, and several polynucleotides including DNA and polyinosinic acid. C1q-p was found to partition with IgG during precipitation by ammonium sulfate and low ionic strength buffer as well as during column chromatography on DEAE-cellulose and G-200 Sephadex. Like AHGG, but in complete contrast to the polynucleotides, the C1q-precipitating activity of C1q-p was sensitive to pepsin, trypsin, and acidic conditions, but unaffected by DNAse or RNAse; the C1q-precipitating activity of anti-C1q antibody was not diminished by any of these procedures. Thus, C1q-p consists of gamma-migrating protein of low m.w., and its C1q-precipitating activity is indistinguishable from that of AHGG. These results are consistent with the concept that C1q-p is comprised, at least in part, of IgG that binds C1q via the Fc portion of the molecule.