Progressive multifocal leukoencephalopathy (PML) in a patient with silicosis treated previously with steroids. A report of a case with JC virus infection confirmed immunohistochemically and by electron microscopy.

We present a case of progressive multifocal leukoencephalopathy (PML) diagnosed at autopsy, in which JC virus infection of the central nervous system was confirmed by means of electron microscopy and immunohistochemistry. The patient had been receiving steroid hormones due to suspected sarcoidosis or pneumoconiosis. Diffuse silicosis in lungs and in hilar and mediastinal lymph nodes was diagnosed at autopsy. Intranuclear inclusions, ultrastructurally typical of JC virus were found in some oligodendrocytes in the white matter. However the strongest immunopositive viral deposits were found in the cerebellar cortex, also within Purkinje cells. Numerous apparently apoptotic cells seen in white matter suggest that this mechanism of cell elimination plays an important role in PML pathogenesis and hence anti-apoptotic treatment may alleviate the symptoms and prolong survival.