PML is a complex disease with many variables to consider when assessing risk. #ClinicSpeak #MSBlog
"The single case report on a 55-year old man with PML and no underlying risk factors highlights the the issue that PML can occur in immuno-competent individuals. This has implications for assessing risk in pwMS on DMTs and in general. Firstly, it makes it impossible to say that drug x, or drug y, is not associated with some PML risk, albeit a very small risk, of developing PML. I have often been taken to task by certain Pharma reps because of this position; they obviously want to control the messaging around their drug and I want to be honest. In short no DMT has zero risk of PML. In my career as a neurologist, I have seen three patients with PML with no apparent underlying immune disorder. All three of these patients were old, in fact they were all over 70 years of age. Presumably immuno-senescence, or an aged immune system, is a risk factor for PML. This is playing out in the MS space as well, where age is emerging as a risk factor as well. This is why we need to be wary about relatively low levels of lymphopaenia in pwMS who are over the age of 60, i.e. between 500 and 800 per mm3."
Grewal et al. Progressive multifocal leukoencephalopathy in a patient without apparent immunosuppression. Journal of NeuroVirology First online: 06 June 2016
Progressive multifocal leukoencephalopathy (PML) is a viral demyelinating disease due to the reactivation of the JC virus (JCV), which usually occurs in the context of immunosuppression in HIV infection, malignancy, or in patients on disease modifying therapy for autoimmune diseases, such as multiple sclerosis (MS) and Crohn's disease. Notably, there is growing recognition that PML can occur in patients with transient immune dysfunction. Here, we present a case of a 55-year-old man without history of immunosuppression or evidence of ICL who was diagnosed with PML on brain biopsy. We will discuss the potential etiologies of mild and transient immunosuppression that can lead to PML with non-apparent immunosuppression.