Table 1 Conditions associated with affecting the prevalence and severity of CSU
From: Stress, pseudoallergens, autoimmunity, infection and inflammation in chronic spontaneous urticaria
Variable | Contribution to CSU | Outline of purported mechanism |
|---|---|---|
Autoimmunity | Predisposing factor | CSU is more frequent in females, associated with a positive autologous serum skin test and is frequently associated with underlying autoimmunity and altered T cells subsets. Diversely autoreactive IgE and IgG autoimmunity is particularly frequent in CSU. Benefit with anti-IgE therapy suggests direct ability of IgE auto-antibodies in triggering mast cell degranulation |
Pseudoallergens | Facilitating factor | These low molecular weight compounds may bind to mast cell Mas related G protein coupled receptor X2 and lower the threshold for other factors to fully activate the mast cells to release CSU mediators. Salicyclates and non-steroidal anti-inflammatory drugs in predisposed individuals increase overall leukotriene activity by COX-1 inhibition. These then lead to mast cell activation and increased CSU activity |
Stress | Facilitating or predisposing factor | Increased inflammation with altered T cell subsets and a reduction in Tregs especially leading to impaired B cell control. Stress released neuropeptides can also activate mast cells via Mas related G protein coupled receptor X2 |
Parasitic infection | Predisposing factor | Parasites stimulate humoral autoimmunity especially a polyclonal IgE which may have auto-reactive components |
Helicobacter gastritis | Predisposing factor | While the frequency of helicobacter infection may be higher in CSU patients evidence of anti-helicobacter therapy being effective is conflicting |
Metabolic syndrome | Co-morbid condition | Both CSU and metabolic syndrome are associated with increased background inflammation. As such the association between these may be due to the chronic inflammation being common to both |
Hypertension | Co-morbid condition | CSU more likely to be prolonged in patients with hypertension; hazard ratio 0.71 |
Dysbiosis of gastrointestinal tract | Predisposing factor | Reductions in several types of bacteria in the stools of those with CSU but not enterobacteriaceae. Altered bowel microbiota may lead to increased gut epithelial permeability and absorption of immune activating compounds |
Vitamin D3 | Facilitating factor | Low levels found in CSU. Vitamin D3 reduces Th1 and Th17 cells and increases T regulatory cell function that can reduce autoimmunity and reduce inflammation |