Most DMTs except glatiramer acetate have well-established (and possibly nonlinear) effects on the numbers of circulating leukocytes; most relevant here are fingolimod (lymphopenia/monocytosis) [31], natalizumab (lymphocytosis) [32], cyclophosphamide (lymphopenia), and interferon-beta (lymphopenia/neutropenia) [33], effects that are confirmed from our data (Table 2). The gene discussed is IFNB1; the disease is lymphopenia.