Chronic urticaria and the pathogenic role of mast cells.

The signs and symptoms of chronic urticaria (CU) are caused by the activation and degranulation of skin mast cells (MCs). Recent studies have added to our understanding of how and why skin MCs are involved and different in CU. Also, novel and relevant mechanisms of MC activation in CU have been identified and characterized. Finally, the use of MC-targeted and MC mediator-specific treatments has helped to better define the role of the skin environment, the contribution of specific MC mediators, and the relevance of MC crosstalk with other cells in the pathogenesis of CU. Here, we review these recent findings and their impact on our understanding of CU, with a focus on chronic spontaneous urticaria (CSU). Also, we highlight open questions, issues of controversy, and unmet needs, and we suggest what studies should be performed moving forward.

Stepping Down Treatment in Chronic Spontaneous Urticaria: What We Know and What We Don't Know.

In chronic spontaneous urticaria (CSU), wheals, angioedema, or both appear spontaneously for > 6 weeks. Current recommended treatment options for urticaria target mast cell mediators such as histamine, or activators, such as autoantibodies. The goal of CSU treatment is to treat the disease until it is gone as effectively and safely as possible. As no cure is available for CSU as of now, the treatment is aimed at continuously suppressing disease activity, with complete control of the disease and a normalization of quality of life. To achieve this, pharmacological treatment should be continued until no longer needed. Treatment of CSU should follow the basic principles of treating as much as needed and as little as possible taking into consideration that the activity of the disease may vary. Since CSU is a disease with spontaneous remission, it is hard to tell, in patients with complete control and no signs or symptoms, when medication is no longer needed. The current international guideline for urticaria suggests that the treatment can be stepped down once a patient is free of signs and symptoms. Other reasons for stepping down the treatment of CSU patients include safety concerns or issues, pregnancy or wanting to become pregnant, and economic factors. As of now, it is unclear over which period, with what intervals and with which dosages CSU treatment should be stepped down. Guidance on this is needed for all recommended therapies: (i) standard-dosed second-generation H1-antihistamine (sgAH), (ii) higher than standard-dosed sgAH, (iii) standard-dosed omalizumab, (iv) higher than standard-dosed omalizumab, and (v) cyclosporine. However, there is a lack of controlled trials on the step down and discontinuation of these treatments. Here, we aim to provide a summary of what is known and what needs to be investigated in further studies, based on our own experience and real-world evidence.