Effect of Polyethylene Glycol-Modified Adenosine Deaminase (PEG-ADA) Therapy in Two ADA-Deficient Children: Measurement of Erythrocyte Deoxyadenosine Triphosphate as a Useful Tool

Abstract

Adenosine deaminase (ADA) deficiency is usually associated with severe combined immunodeficiency (SCID) and results in clinical, immunological and biochemical abnormalities. Biochemical abnormalities are characterized by accumulation of purine metabolites; adenosine, deoxyadenosine, dADP and dATP in biological fluids and cells,^1,2. Untreated this disease is usually fatal during the first few months of life. The therapy of choice is bone-marrow transplantation from histocompatible donors³. Unfortunately in most instances, HLA-identical donors are not available. Thus others therapeutic approaches including gene therapy have to be considered. Enzyme replacement therapy in the form of repeated red cell transfusions has been of clinical benefit in some children but the response is often unsustained⁴. Recently, a new enzyme replacement therapy, polyethylene glycol-modified bovine ADA has been tested in some children with ADA deficiency and SCID⁵.