Human ADA2 (adenosine deaminase 2) deficiency (DADA2) is an inborn error of immunity with a broad clinical phenotype, which encompasses vasculopathy and hemato-immunological features. Diagnosis is based on the combination of decreased serum ADA2 activity and the identification of biallelic deleterious alleles in the ADA2 gene. DADA2 carriers harbor a single pathogenic variant in ADA2 and were mostly considered healthy and asymptomatic. We investigated the effect of several reported ADA2 missense variants on ADA2 protein expression, secretion, and enzymatic activity. Our studies indicate that p.G47A, p.G47R, p.G47V, p.R169Q, p.E328K, p.H424N, and p.Y453C exert a dominant negative effect on ADA2 enzymatic activity, dimerization, and/or secretion. We conclude that humans with heterozygous dominant negative missense variants in ADA2 are at risk of DADA2.

Isabelle Meyts is invited by Jérome Delon.