Epigenetic alterations on C1-inhibitor expression may influence hereditary angioedema attack frequency and C4 levels.

Khan, Sujoy; Longhurst, Hilary

The interesting report by Karagianni P et al on the finding of increased DNA methylation of H19 locus imprinting control region in saliva samples of Sjögren's syndrome patients correlating with low complement C4 levels [1], may offer insights into how C4 level may be regulated in serpinopathies such as C1-inhibitor deficiency. An undetectable or low C4 level in patients with severe angioedema is a feature of C1-inhibitor deficiency (hereditary angioedema (HAE) type I with low to absent function and antigenic levels; HAE type II with point mutations in SERPING1 gene that affect the reactive centre loop affecting protein function only).