Neurologic Abnormalities in Patients with Adenosine Deaminase Deficiency

Defects in adenosine deaminase enzyme cause severe immunodeficiency. Without enzyme replacement or allogeneic bone marrow transplantation, patients often suffer fatal infection in infancy. Adenosine deaminase is expressed ubiquitously; deficiency may affect various organs, including the brain. Neurologic abnormalities occur in some adenosine deaminase-deficient patients, mostly in association with infection or after bone marrow transplantation. Three cases with significant neurologic abnormalities, including hypotonia, head lag, nystagmus, difficulty in focusing gaze, seizure disorder, and moderate-severe developmental delay but with no evidence of infection or transplant-related medication toxicity are presented. Computed tomographic scans and cranial MRI revealed volume loss and abnormalities of basal ganglia and thalamus, which may reflect accelerated nerve cell death or altered stimulation of adenosine receptors. Detailed neurologic and neuroimaging evaluation should be performed for all patients with adenosine deaminase deficiency upon diagnosis, to identify potentially significant brain lesions.