Report of the Canadian Expert Committee on the management of ADA deficiency

Adenosine deaminase (ADA) deficiency is a form of severe combined immunodeficiency. Aberrant mutations in the ADA gene result in loss of ADA activity and the toxic accumulation of metabolites that damage both immune and non-immune organs. While patients with complete ADA deficiency present during infancy with failure to thrive, recurrent bacterial, viral and fungal infections, those with incomplete (partial) deficiency may present at a later age with milder symptoms associated with reduced T, B, and NK cell subpopulations. Based on experience in Canadian centres, we provide management guidelines for patients with ADA deficiency, including a treatment algorithm for use of hematopoietic stem cell transplantation, gene therapy, and enzyme replacement therapy. Statement of novelty: Herein, we define guidelines for the management and treatment of patients with ADA deficiency.