Progressive multifocal leukoencephalopathy
| Progressive multifocal leukoencephalopathy | |
|---|---|
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| T2-weighted MRI showing progressive multifocal leukoencephalopathy | |
| Classification and external resources | |
| Specialty | infectious disease |
| ICD-10 | A81.2 |
| ICD-9-CM | 046.3 |
| DiseasesDB | 10718 |
| MedlinePlus | 000674 |
| eMedicine | radio/573 |
| MeSH | D007968 |
Progressive multifocal leukoencephalopathy (PML) is a rare and usually fatal viral disease characterized by progressive damage (-pathy) or inflammation of the white matter (leuko-) of the brain (-encephalo-) at multiple locations (multifocal). It is caused by the JC virus, which is normally present and kept under control by the immune system. JC virus is harmless except in cases of weakened immune systems. In general, PML has a mortality rate of 30–50 percent in the first few months and those who survive can be left with varying degrees of neurological disabilities.
PML occurs almost exclusively in patients with severe immune deficiency, most commonly among patients with acquired immune deficiency syndrome (AIDS), but people on chronic immunosuppressive medications including chemotherapy are also at increased risk of PML, such as patients with transplants, Hodgkin's Lymphoma, multiple sclerosis, psoriasis and other autoimmune diseases.
Symptoms can develop over several weeks to months. Symptoms depend on location of damage in the brain and the degree of damage. The most prominent symptoms are "clumsiness, progressive weakness and visual, speech, and sometimes personality changes" The lesions affecting the parietal and occipital lobes can lead to a phenomenon known as alien hand syndrome.
The cause of PML is a type of polyomavirus called the JC virus (JCV), after the initials of the person from whose tissue the virus was first successfully cultured. Recent publications indicate 39% to 58% of the general population are seropositive for antibodies to JCV, indicating current or previous infection with the virus. Other publications put the percentage at 70% to 90% of the general population. JCV causes persistent asymptomatic infection in approximately one-third of the adult population, based on viral shedding into the urine from the site of asymptomatic infection in the kidney. The virus causes disease only when the immune system has been severely weakened.
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