Information related to physical urticaria types
According to the time of evolution of urticaria it can be classified in acute a chronic. Acute urticaria has duration of less than six weeks, the involution of this condition is and there are no subsequent relapses. Chronic urticaria lasts more than six weeks. Another way to classify urticaria can be done considering its pathophysiological mechanism, however on this classification it can be found very often overlap and redundancy since some types of urticaria can fall inside one or more categories.
Considering the immunological mechanism, urticaria can be classified as:
- Urticaria due to complement factors.
- Urticaria for immunoglobulins or immune complexes.
- Non immunologic urticaria due to the direct or indirect effect of substances which favor the degranulation of mast cells.
The concept of autoimmune urticaria and its association with the presence of histamine releasing antibodies has been developed during the last decade. A detailed clinical, immunologic and histological study made on the year 1986 to twelve patients affected with chronic idiopathic urticaria has shown that after the intradermal injection of autologous serum triggered the formation of hives, which is not observed on healthy individuals and it has been postulated the presence of a factor in the serum related to the activity of the condition and which could be important for its pathogenesis. About fifty percent of patients with chronic urticaria can have circulating antibodies.
The releasing of histamine of the basophilic is right now the most important parameter to detect functional antibodies on the serum of patients with chronic urticaria. The cutaneous test of the autologous serum is the best in vivo test to detect the activity of the basophilic releaser of histamine in vitro. This test has a sensibility of seventy percent and a specificity of about eighty percent when an erymathous papule (hive) of 1.5 millimeters is read, this hive is induced by the autologous serum applied trough intradermal route on the forearm with an adjacent saline control in thirty minutes.
The findings of basophilic elements on peripheral blood in low quantities or absent in patients with chronic urticaria with antibodies releasers of histamine can be a clinical sign for autoimmune urticaria. The clinical presentation of patients with or without antibodies is very similar, although those patients with antibodies tend to be affected with a more severe manifestation of autoimmune urticaria. The identification of this subgroup of patients has practical implications on the treatment of the condition with immunotherapy.
Some studies refer that some patients with chronic idiopathic urticaria shown evidence of thyroid autoimmunity of about fourteen percent compared with an expected prevalence of six percent on general population. Autoimmune conditions (such as diseases affecting thyroid gland, pernicious anemia, rheumatoid arthritis and insulin-dependent diabetes among others) were associated more frequently with patients affected by chronic urticaria which also had functional antibodies.
The diagnosis of urticarial vasculitis is defined by the presence of hives for more than twenty four hours for even more than seven days.