Atypical Presentation of Progressive Multifocal Leukoencephalopathy in a Natalizumab-treated Patient (P4.033)

BACKGROUND: Natalizumab is one of the most effective treatment in relapsing-remitting Multiple Sclerosis (RR-MS). Its use may be complicated by the occurrence of progressive multifocal leukoencephalopathy (PML) due to JC virus (JCV) reactivation. CASE REPORT: A 28 year-old man affected by RR-MS showed MRI findings compatible with PML (left thalamic lesion without contrast enhancement) during treatment with Natalizumab (just after course 24th), in absence of neurological signs or symptoms. Interferon beta-1a was the only previous therapy. Natalizumab was immediately interrupted and JCV-DNA was detected in cerebrospinal fluid (viral loads of 12 copies/mL). Three plasma-exchange were performed and mirtazapine administered. For the next two months patient remained asymptomatic and underwent a strict MRI follow up (one MRI every 2 weeks) with no changes. On October 2014 right-hand weakness and hypoesthesia suddenly occured, followed by right leg paresis with gait impairment. A new MRI showed enlargement of the thalamic lesion, extending to upper white matter along the cortico-spinal tract up to the cortical prerolandic area and no contrast enhancement. Considering the probable late worsening of PML, anti-edema drugs were administered with partial recovery. Two weeks later a new MRI showed contrast enhancement of all the previous MS lesions and partially of the PML lesion, without a further dimension increase; moreover a new lesion of the left upper cerebellar peduncle appeared. Being the findings consistent with PML-immune reconstruction inflammatory syndrome (IRIS), high dose intravenous steroids were administered. CONCLUSIONS: Pauci- or a-symptomatic PML should be strictly clinically and radiologically followed-up because of the possible rapid worsening even after a long period of stability. After some months from PML diagnosis, physicians should take into account that neurological worsening could be due to PML extension as well as to IRIS occurrence. Disclosure: Dr. De Mercanti has nothing to disclose. Dr. Artusi has nothing to disclose. Dr. Clerico has nothing to disclose. Dr. Iudicello has nothing to disclose. Dr. Vacca has nothing to disclose. Dr. Virgilio has nothing to disclose. Dr. Durelli has nothing to disclose.