Rare connective tissue diseases are more prevalent in people with hereditary angioedema (HAE) than in the general population, according to a new study from Italy. This study is the first to explore the prevalence of these diseases in HAE patients.
The diseases examined include lupus, Sjögren’s disease, systemic sclerosis (SSc), and antiphospholipid syndrome (APS). Researchers found that these diseases occur about 5 to 10 times more frequently in individuals with HAE compared to the general population.
The study titled “Rare connective tissue diseases in patients with C1-inhibitor deficiency hereditary angioedema: first evidence on prevalence and distribution from a large Italian cohort study” was published in the journal Frontiers in Immunology.
In HAE, genetic mutations disrupt the production of the C1-inhibitor protein (C1-INH). This protein is essential for controlling bradykinin, a molecule involved in inflammation and blood pressure. Without enough C1-INH, bradykinin levels rise, causing fluid to leak from blood vessels and resulting in swelling episodes.
C1-INH also regulates the complement system, a group of immune proteins that help fight infections and manage inflammation. A deficiency in C1-INH can throw off the balance of these proteins, potentially making HAE patients more likely to develop autoimmune diseases, such as lupus and SSc.
The study involved 855 HAE patients from the Italian Network for Hereditary and Acquired Angioedema registry. Most participants had HAE type 1, which is characterized by insufficient C1-INH production. The study showed that 2.1% of these patients were diagnosed with a rare connective tissue disease.
Lupus was the most common co-occurring disease, affecting eight patients. The prevalence of lupus in HAE patients was 0.94%, compared to an estimated 0.04% in the general population. The prevalence of APS and SSc was also higher in HAE patients than in the general population. The study noted that the prevalence of Sjögren’s disease in HAE patients was similar to that in the general population.
Out of the eight lupus cases, most occurred in women. Symptoms included skin inflammation, kidney issues, and low blood cell counts. All affected individuals received immunosuppressants, achieving stable remission.
Four HAE patients had Sjögren’s disease, all of whom were women. These patients showed signs of dry eyes and dry mouth, and two had joint arthritis. Three patients had APS, with signs such as lupus anticoagulant and recurrent blood clots.
The findings provide crucial evidence on the prevalence of rare connective tissue diseases among HAE patients. The data highlights a significant link between HAE and these autoimmune conditions.
