Acute leukocytosis during alemtuzumab treatment in patients with active relapsing-remitting multiple sclerosis

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system and is one of the main causes of disability in young adults. Alemtuzumab is a humanized monoclonal anti CD52 antibody approved for active relapsing-remitting (RR) multiple sclerosis (MS) exerting its strong clinical efficacy by a specific pattern of depletion of CD52-positive immune cells followed by their repopulation. As with most infused biological therapies, infusion-associated reaction (IAR) are frequently reported as adverse events for alemtuzumab treatment. In addition to cellular depletion, bystander effects including transient cell activation and triggered cytokine release are thought to cause alemtuzumab-specific IARs. We describe acute laboratory changes during first alemtuzumab infusion week in a RRMS patient, underling acute changes in immunological and routine laboratory parameters.