PECAM1 and cerebellar ataxia: Lymphopenia (630/μL; RV: 1400-5500*).Low CD4+ (25%; RV: 28.1-43.2***) and low %CD45RA+CD31+T cells (3.9%; RV: 53.2-67.5***).Normal IgG, IgA and IgM. Reduced proliferation assays.Ataxia, telangiectasia of the eyes.