Hereditary Angioedema with Normal C1 Inhibitor: An Italian Case Series


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Hereditary angioedema with normal C1-inhibitor (nC1-INH-HAE) with and without factor XII mutations (FXII-HAE and U-HAE respectively) are familial disorders. We present the genetic and clinical features of patients with nC1-INH-HAE followed up in centers of the Italian Network for Angioedema (ITACA). 97 patients with personal or family history of angioedema and normal plasma levels of C1 inhibitor were studied. All patients were investigated for mutations in the whole F12 gene coding region by direct DNA sequencing. 80 patients had angioedema symptoms. Of these patients, 20 females (median age 42.2 years, range 12-78), belonging to 8 unrelated families, had the same mutation in F12 gene, leading to the most common disease-causing aminoacid substitution, p.Thr309Lys. They were diagnosed as FXII-HAE. The haplotype analysis by using intragenic SNPs confirmed the hypothesis of a common founder. 17 subjects (9 males) in 7 FXII-HAE families were asymptomatic carriers of the same mutation. 60 patients (38% males; median age 45 years, range 12-81) had history of angioedema in their 36 families and no mutation in F12 gene. They were diagnosed as U-HAE. Sequencing analysis revealed the presence of different SNPs that have been previously described as not affecting protein activity or function. Accordingly, the minimum prevalence of FXII-HAE and U-HAE in Italy in 2016 is 37:59.394.000 inhabitants and 60:59.394.000 respectively, equivalent to 1:1.605.243 for FXII-HAE and 1:989.900 for U-HAE. This nationwide survey of C1-INH-HAE provides for Italy a prevalence lower than in other European countries. We hyphotesize a disomogeneous geographical distribution of nC1-INH-HAE among European countries.
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normal c1 inhibitor
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