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       #Post#: 820--------------------------------------------------
       (CMSC) Tysabri-related PML case w/repeated negative anti-JCV ant
       ibody testing
       By: agate Date: June 7, 2015, 1:39 pm
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       Presented at the CMSC (Consortium of Multiple Sclerosis Centers)
       conference, May 29, 2015:
       [quote]1: 10,000 Is Not Zero. Lessons Learned from a
       Natalizumab-Related PML Case with Repeated Negative Anti-JCV
       Antibody Testing
       Marie-Sarah Gagne Brosseau, MD , Neurology, University of
       Washington, Seattle, WA
       Gary Stobbe, MD , Neurology, University of Washington, Seattle,
       WA
       Deb Cramer, RN , Neurology, University of Washington, Seattle,
       WA
       Hillary Lipe, A.R.N.P. , Neurology, University of Washington,
       Seattle, WA
       Annette Wundes, MD , Neurology, University of Washington,
       Seattle, WA
       PDF
       Background:
       Progressive multifocal leukoencephalopathy (PML) is a severe
       brain infection caused by the JC virus (JCV) that leads to lysis
       of oligodendrocytes. Natalizumab is known to be associated with
       PML. Clinical presentation varies; most common symptoms are
       cognitive impairment, weakness and language deficit.
       Natalizumab-related PML has a mortality rate of 22% and many
       survivors have a poor functional outcome, which makes it
       natalizumab’s most serious complication.
       50-60% of adults have detectable serum antibodies against JCV.
       Seropositivity for anti-JCV antibodies is a PML risk factor and
       periodic testing is recommended. Previously, 2
       natalizumab-treated multiple sclerosis PML patients were
       classified as anti-JCV antibody negative, but testing dated from
       8 and 9 months before diagnosis.
       Objectives:
       To describe a case of natalizumab-associated PML in which the
       last anti-JCV antibody testing 2 weeks before onset of symptoms
       was negative.
       Methods:
       Case presentation.
       Results:
       A 70-year-old woman with multiple sclerosis (MS) treated with
       natalizumab for 4.5 years developed PML symptoms of right hand
       weakness 2 weeks after last negative anti-JCV antibody testing.
       She had never received immunosuppressants. Brain MRI showed 4
       new nonenhancing lesions which were surmised due to MS. A course
       of intravenous methylprednisolone for a presumed relapse was
       given but her weakness worsened. Short-term repeat MRI was
       suggestive of PML and CSF JCV PCR came back positive. While 4
       prior quantitative anti-JCV antibody tests every 3 months had
       been negative, including 2 weeks prior to onset of symptoms
       (index 0.19), at time of diagnosis the result was positive
       (index 2.56). Evolution and management of the present case will
       be presented.
       Conclusions:
       Initial misdiagnosis of MS relapse may delay the diagnosis of
       PML. Clinicians should be wary that a natalizumab-treated
       patient with new MRI findings and/or neurological symptoms could
       have PML, including those with negative anti-JCV antibody. 2
       weeks is currently the shortest interval reported between last
       negative anti-JCV antibody testing and onset of PML symptoms. In
       negative patients, risk can be due to a false negative test
       result reported as 3%, or to de novo infection. In our case, de
       novo infection with seroconversion is more plausible given the
       repeatedly negative testing. If PML is suspected, anti-JCV
       antibodies should be repeated even if recently negative.
       Moreover, short-term repeat MRI and CSF testing warrant
       consideration.[/quote]
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