As CD52 is also expressed on the surface of non-malignant mature lymphocytes, treatment with alemtuzumab and associated lymphodepletion can lead to life-threatening infectious complications, including reactivation of cytomegalovirus (CMV), JC-virus-related progressive multifocal leukoencephalopathy (PML), fungal infections, and non-opportunistic infections [9,10]. The gene discussed is CD52; the disease is progressive multifocal leukoencephalopathy.