Consensus approach for the management of severe combined immune deficiency caused by adenosine deaminase deficiency

Inherited defects in adenosine deaminase (ADA) cause a subtype of severe combined immunodeficiency (SCID), known as ADA-SCID. Most affected infants can be diagnosed while still asymptomatic by a SCID newborn screening test, allowing early initiation of therapy. We reviewed the evidence currently available and propose a consensus management strategy. In addition to the treatment of the immune deficiency of ADA-SCID, patients should be followed for specific non-infectious respiratory, neurological and biochemical complications associated with ADA deficiency. All patients should initially receive enzyme replacement therapy (ERT), followed by definitive treatment with either of two equal first line options. If an HLA matched sibling donor (MSD) or matched family donor (MFD) is available, allogeneic hematopoietic stem cell transplantation (HSCT) should be pursued. The excellent safety and efficacy observed in over 100 ADA-SCID patients who received gamma-retrovirus or lentivirus mediated autologous hematopoietic stem cell gene therapy (HSC-GT) since 2000 now positions HSC-GT as an equal alternative. If MSD/MFD HSCT or HSC-GT are not available or have failed, ERT can be continued or re-instituted, and HSCT using alternative donors should be considered. The outcomes of novel HSCT, ERT and HSC-GT strategies should be evaluated prospectively in "real life" conditions to further inform these management guidelines.