ADA2 genotype and enzyme activity may predict vasculitic or hematologic DADA2 phenotype

Deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease with diverse phenotypes. We describe the genetics, phenotypes, and treatment of n = 48 DADA2 patients from Germany, Austria, and Switzerland. We report a high incidence of hematological (83%) and immunological features (85%), a comparatively low anti-tumor necrosis factor full-response rate (58%), and a high decision probability (21%) for hematopoietic cell transplantation (HCT). We establish a correlation between genetic variant ADA2 activity and patient ADA2 activity. Remarkably, lower patient ADA2 activity is predictive of neutropenia and shows a trend toward HCT decision, whereas higher patient ADA2 activity is predictive of vasculitis symptoms. Genetic variants with low residual ADA2 activity are significantly more common among patients receiving HCT. Our study corroborates previous observations connecting ADA2 activity and clinical phenotype, which up to now have been mainly based on in vitro data.