IRIS without PML in MS patients - a case report of IRIS after past alemtuzumab therapy with subsequent oral cladribine treatment and review of the literature.

Alemtuzumab is a high-efficacy drug for relapsing-remitting multiple sclerosis (MS), leading to non-selective reconstitution of the immune system. Immune reconstitution inflammatory syndrome (IRIS) develops due to reconstruction of cellular immunity and inflammation in the CNS, mostly after progressive multifocal leukoencephalopathy (PML). A case of a 42-year-old patient is presented treated in the past with alemtuzumab because of highly active MS. He was admitted after 8 years of remission because of aphasia, bulbar syndrome and severe agitation. MRI of the brain showed multiple big confluencing lesions supra- and infratentorially, with mass effect and contrast enhancement. IRIS was diagnosed. Prolonged steroids therapy and plasma exchange were used with success. IRIS can also be a complication of natalizumab or fingolimod withdrawal and arise from the restoration of the previously suppressed immune response. Other cases of IRIS in MS patients without preceding PML are also reviewed.