Observational Study on Characteristics and Survival Correlates of Progressive Multifocal Leukoencephalopathy (PML) in Italy

The goal of this observational study is to learn about the features of Progressive Multifocal Leukoencephalopathy (PML) at the time of its diagnosis and the factors that may influence the outcome of persons with this disease. PML is a rare and rapidly progressive disease of the brain, caused by a virus named JC polyomavirus (JCV). This disease almost always occurs in persons with an immune dysfunction. In some people, the underlying immune dysfunction may be the consequence of other conditions, such as certain hematological tumors (for instance, some lymphomas) or the infection with the Human Immune Deficiency Virus (HIV). In other cases it may be associated with other forms of immune deficiency, either present at birth or acquired later in life, or with immunosuppressive or immunomodulant treatments, such as Natalizumab in persons with Multiple Sclerosis. Unfortunately, there is no cure for PML, and the only possibility to stop the progression of the disease is to eliminate the cause of the underlying immune dysfunction. This is not always possible, or it may take time, and, therefore, more than half of the persons who developed PML will not survive to the disease. This study takes advantage of the systematic collection, over a time frame of 37 years, of the characteristics of 456 cases of PML. The main question of this study aims to answer whether and how PML characteristics and outcome have evolved over time and also according to the disease or condition that caused the immune dysfunction leading to PML. This is important because PML is a rare disease, and, therefore, knowing the context in which it develops can be useful for healthcare providers and families to consider PML as a possible cause of unexpected neurological problems. In fact, an early recognition of PML is associated with a better outcome. On the other hand, there are clinical and laboratory features of PML that can also be associated with different disease outcome. Therefore, it is important th