Chronic Idiopathic Urticaria
Chronic Idiopathic Urticaria
Purpose of Review: Chronic idiopathic urticaria has long been a demoralizing disease, baffling allergists and dermatologists alike, to the detriment of the patient. Recent findings, however, have shed light on causation in many, though not all, of these patients. The purpose of this review is to bring the reader up to date on the current position regarding aetiology and pathogenesis and the strength of the evidence. The review also seeks to point up rational approaches to diagnosis and treatment in the light of these developments.
Recent Findings: Chronic idiopathic urticaria encompasses at least two subgroups. One of these is the now well-established entity of autoimmune chronic urticaria, due to autoantibodies against either the high-affinity IgE receptor FcεR1 or, less commonly, IgE. These patients, who co-segregate with chronic idiopathic urticaria patients having an increased frequency of antithyroid autoantibodies, represent 30-50% of the patients previously desigated as having chronic idiopathic urticaria. Convenient routine diagnostic tests for this subset remain elusive. The remaining 50% of patients with chronic idiopathic urticaria remain truly 'idiopathic', although the condition in some may have an autoimmune basis, autoantibodies having eluded current techniques for detection. Selected patients with autoimmune urticaria may benefit from immunotherapy.
Summary: It is now known that in 30-50% of patients with chronic idiopathic urticaria, the condition has an autoimmune basis, although confirmation of the diagnosis in these patients is not straightforward. In selected patients, attempts to establish this diagnosis are worthwhile since there are important therapeutic implications.
Chronic idiopathic urticaria (CIU), defined as the occurrence of daily, or almost daily, wheals and itching for at least 6 weeks, with no obvious cause, has not been the subject of detailed epidemiological studies. Published figures for frequency are confounded by uncertainty of the diagnosis, since the term 'chronic idiopathic urticaria' is often taken to encompass physical urticarias as well as CIU. However, a figure of 0.5% for the lifelong prevalence is probably not wide of the mark and this figure does not seem to vary greatly across different regions of the world. In any case, it is widely acknowledged that CIU is a major affliction causing serious disability to a degree equal to that experienced by sufferers form triple coronary arterial disease.
Physical urticarias, especially delayed pressure urticaria, also frequently occur concurrently with CIU in the same patients, and the prognosis and treatment for these two very different types of chronic urticaria may also be very different. It is therefore important to tease these entities out from the patient's history and clinical assessment, in order to determine which urticarial disorder is principally responsible for the patient`s disabilities. About 90% of patients with CIU also have angio-oedema, and, in the ensuing text, the abbreviation CIU includes both entities.
The major advance in our understanding of CIU in recent years has been the discovery that in 30-50% of patients with CIU the disease is due to an autoimmune process, and therefore is not strictly 'idiopathic'. In autoimmune urticaria, circulating IgG autoantibodies react specifically with the α-chain of the high-affinity IgE receptor on dermal mast cells and basophils, evoking release of histamine and other mediators, which cause urticaria and angio-oedema. The remainder of this review deals with the differential diagnosis of CIU, the pathophysiology of autoimmune chronic urticaria (AICU) and its diagnosis, significance, clinical and laboratory features and treatment. The problem of patients with CIU that is not autoimmune is also discussed, and approaches to its investigation and management are proposed. These issues have been reviewed elsewhere recently.
Abstract and Introduction
Purpose of Review: Chronic idiopathic urticaria has long been a demoralizing disease, baffling allergists and dermatologists alike, to the detriment of the patient. Recent findings, however, have shed light on causation in many, though not all, of these patients. The purpose of this review is to bring the reader up to date on the current position regarding aetiology and pathogenesis and the strength of the evidence. The review also seeks to point up rational approaches to diagnosis and treatment in the light of these developments.
Recent Findings: Chronic idiopathic urticaria encompasses at least two subgroups. One of these is the now well-established entity of autoimmune chronic urticaria, due to autoantibodies against either the high-affinity IgE receptor FcεR1 or, less commonly, IgE. These patients, who co-segregate with chronic idiopathic urticaria patients having an increased frequency of antithyroid autoantibodies, represent 30-50% of the patients previously desigated as having chronic idiopathic urticaria. Convenient routine diagnostic tests for this subset remain elusive. The remaining 50% of patients with chronic idiopathic urticaria remain truly 'idiopathic', although the condition in some may have an autoimmune basis, autoantibodies having eluded current techniques for detection. Selected patients with autoimmune urticaria may benefit from immunotherapy.
Summary: It is now known that in 30-50% of patients with chronic idiopathic urticaria, the condition has an autoimmune basis, although confirmation of the diagnosis in these patients is not straightforward. In selected patients, attempts to establish this diagnosis are worthwhile since there are important therapeutic implications.
Chronic idiopathic urticaria (CIU), defined as the occurrence of daily, or almost daily, wheals and itching for at least 6 weeks, with no obvious cause, has not been the subject of detailed epidemiological studies. Published figures for frequency are confounded by uncertainty of the diagnosis, since the term 'chronic idiopathic urticaria' is often taken to encompass physical urticarias as well as CIU. However, a figure of 0.5% for the lifelong prevalence is probably not wide of the mark and this figure does not seem to vary greatly across different regions of the world. In any case, it is widely acknowledged that CIU is a major affliction causing serious disability to a degree equal to that experienced by sufferers form triple coronary arterial disease.
Physical urticarias, especially delayed pressure urticaria, also frequently occur concurrently with CIU in the same patients, and the prognosis and treatment for these two very different types of chronic urticaria may also be very different. It is therefore important to tease these entities out from the patient's history and clinical assessment, in order to determine which urticarial disorder is principally responsible for the patient`s disabilities. About 90% of patients with CIU also have angio-oedema, and, in the ensuing text, the abbreviation CIU includes both entities.
The major advance in our understanding of CIU in recent years has been the discovery that in 30-50% of patients with CIU the disease is due to an autoimmune process, and therefore is not strictly 'idiopathic'. In autoimmune urticaria, circulating IgG autoantibodies react specifically with the α-chain of the high-affinity IgE receptor on dermal mast cells and basophils, evoking release of histamine and other mediators, which cause urticaria and angio-oedema. The remainder of this review deals with the differential diagnosis of CIU, the pathophysiology of autoimmune chronic urticaria (AICU) and its diagnosis, significance, clinical and laboratory features and treatment. The problem of patients with CIU that is not autoimmune is also discussed, and approaches to its investigation and management are proposed. These issues have been reviewed elsewhere recently.
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