The ultimate price of a false diagnosis

In one of the original natalizumab studies a 46-year-old woman unfortunately died from progressive multifocal leukoencephalopathy (PML) after having received 37 doses of natalizumab. Although PML was confirmed at post-mortem there was no pathological evidence that this person had MS.


Kleinschmidt-DeMasters and Tyler. Progressive multifocal leukoencephalopathy complicating treatment with natalizumab and interferon beta-1a for multiple sclerosis. N Engl J Med. 2005 Jul 28;353(4):369-74.


According to the established definition of MS used at the time the patient should probably not have been diagnosed as having MS. The following letter to the journal high-lighted this issue very well.


Berger and Deisenhammer. Progressive multifocal leukoencephalopathy, natalizumab, and multiple sclerosis. N Engl J Med. 2005 Oct 20;353(16):1744-6; author reply 1744-6.


"In all likelihood this patient probably did not have MS. The great tragedy is that she died of a complication of receiving natalizumab." 

"The lesson here is not to rush into making a diagnosis of MS; if there is uncertainty it is better to wait for the disease to fully declare itself. To quote one of my great clinical mentors Professor Tom Bothwell: 'Time is often the best diagnostician'."

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