From the Guidelines
Urticaria is associated with autoantibodies in approximately 30-50% of cases of chronic spontaneous urticaria (CSU), and diagnosis can involve the autologous serum skin test (ASST) or more specialized tests like the basophil activation test or basophil histamine release assay. The presence of autoantibodies, primarily IgG antibodies against the high-affinity IgE receptor (FcεRIα) or against IgE itself, triggers mast cell and basophil activation, leading to histamine release and subsequent development of wheals and angioedema 1.
Diagnosis and Treatment
The diagnosis of autoimmune urticaria can be made using the ASST, where the patient's own serum is injected intradermally to observe for wheal formation, as it offers a reasonably sensitive and specific screening test 1. Treatment for autoimmune urticaria follows a stepwise approach, starting with second-generation H1-antihistamines like cetirizine (10mg daily) or fexofenadine (180mg daily), which can be increased up to four times the standard dose if needed. For refractory cases, omalizumab (300mg subcutaneously every 4 weeks) is highly effective 1.
Immunomodulating Therapies
Immunosuppressive therapies such as cyclosporine (3-5mg/kg/day) may be considered for patients who don't respond to antihistamines or omalizumab, and should be restricted to patients with disabling disease who have not responded to optimal conventional treatments 1. Patients should also be evaluated for underlying autoimmune conditions like thyroid disease, as these are more common in patients with autoimmune urticaria and may require specific management.
Key Considerations
- Approximately 30-50% of CSU patients have functional autoantibodies
- Diagnosis can involve the ASST or more specialized tests
- Treatment follows a stepwise approach, starting with second-generation H1-antihistamines
- Omalizumab is highly effective for refractory cases
- Immunosuppressive therapies should be restricted to patients with disabling disease who have not responded to optimal conventional treatments
- Evaluation for underlying autoimmune conditions like thyroid disease is necessary
From the Research
Urticaria and Autoantibodies
- Urticaria is now recognized as an autoreactive disorder in a substantial fraction of patients, with autoantibodies against the high affinity IgE receptor or IgE detected in about half of these patients 2.
- A serologic mediator of whealing has been demonstrated in 50-60% of patients with chronic urticaria, indicating the presence of autoantibodies 2.
- Autoimmune urticaria is a subgroup of patients presenting with continuous ordinary urticaria, with at least 40% of patients with unexplained (idiopathic) chronic urticaria having clinically relevant functional autoantibodies to the high-affinity IgE receptor on basophils and mast cells 3.
Treatment of Urticaria with Autoantibodies
- The use of immunomodulatory drugs, such as cyclosporine, has been shown to be effective in treating autoimmune urticaria, with a success rate of 70-80% 4.
- Low-dose cyclosporin A has been shown to be an effective and short-term treatment with minimum side-effects in patients with autoimmune urticaria, with 87% of patients being symptom-free at the one-year follow-up 5.
- Antihistamines, such as loratadine or cetirizine, are also effective in treating chronic idiopathic urticaria, with a success rate of 40-55% 4.
- Omalizumab, an anti-IgE antibody, has been shown to be effective in treating antihistamine-resistant cases of chronic spontaneous urticaria, with a success rate of 65-80% 4.
Diagnosis of Autoimmune Urticaria
- The diagnosis of autoimmune urticaria is based on the presence of autoantibodies to the high-affinity IgE receptor or IgE, and a positive autologous serum skin test (ASST) 5, 3.
- The ASST is a useful diagnostic tool for identifying patients with autoimmune urticaria, with a positive result indicating the presence of autoantibodies 5.