Comorbidity of chronic spontaneous urticaria and autoimmune thyroid diseases: a systematic review.

Chronic spontaneous urticaria (CSU) patients are widely held to often have other autoimmune disorders, including autoimmune thyroid disease. Here, we systematically evaluated the literature on the prevalence of thyroid autoimmunity in CSU and vice versa. There is a strong link between CSU and elevated levels of IgG anti-thyroid autoantibodies (AAbs), with most of a large number of studies reporting rates of ≥10%. Levels of IgG against thyroid peroxidase (TPO) are more often elevated in CSU than those of other IgG anti-thyroid AAbs (strong evidence). Levels of IgG anti-thyroid AAbs are more often elevated in adult CSU patients than in children (strong evidence). CSU patients exhibit significantly higher levels of IgG anti-thyroid AAbs (strong evidence) and IgE-anti-TPO (weak evidence) than controls. Elevated IgG anti-thyroid AAbs in CSU are linked to the use of glucocorticoids (weak evidence) but not to disease duration or severity/activity, gender, age or ASST response (inconsistent evidence). Thyroid dysfunction rates are increased in CSU patients (strong evidence). Hypothyroidism and Hashimoto's thyroiditis are more common than hyperthyroidism and Graves' disease (strong evidence). Thyroid dysfunction is more common in adult CSU patients than in children (strong evidence) and in female than male CSU patients (weak evidence). Urticaria including CSU is more prevalent in patients with thyroid autoimmunity than in healthy controls (weak evidence). CSU can improve in response to treatment with levothyroxine or other thyroid drugs (strong evidence). Pathogenic mechanisms in CSU patients with thyroid autoimmunity may include IgE against autoantigens, immune complexes and complement. This article is protected by copyright. All rights reserved.