For example, high serum vitamin B12 is typically elevated in ALPS; brain, lung and gut lesions may characterize CTL4 and LRBA deficiency, and chronic EBV infections are more typical of disorders such as X-linked immunodeficiency with magnesium defect (XMEN, already mentioned in Table 2). The gene discussed is SLC44A4; the disease is Epstein-Barr virus infection.