Successful Resolution of Progressive Multifocal Leukoencephalopathy after Combination Therapy with Cidofovir and Cytosine Arabinoside

SIR—We read the interesting article by Blick et al. [1]. We challenge the conclusions made by the authors. Blick et al. point out that improvement in their patient’s condition was not related to antiretroviral therapy because progressive multifocal leukoencephalopathy (PML) developed 3 months after this treatment was applied. Certainly some opportunistic infections, such as cytomegalovirus retinitis, can develop soon after antiretroviral therapy is started [2]. However, this particular therapy can prevent the development or relapse of cytomegalovirus retinitis [3]. Therefore, the diagnosis of opportunistic infections in the early weeks of antiretroviral treatment does not necessarily mean this treatment will fail in the long term. The immune system needs more time to reconstite itself [4], and the effect of antiretroviral therapy on opportunistic infections might be observed only after improvement of immune status. Some investigators [4] observed improvement in the outcome of PML after antiretroviral therapy. We also observed extended survival in 2 patients who received this treatment (2 and 4 years of follow-up) and were previously diagnosed with PML by cerebral biopsy. The effect of cytosine arabinoside (ara-C) on PML has not yet been proved to be favorable [5]. However, Blick et al. suggest that ara-C and cidofovir, not antiretroviral therapy, caused improvement in their patient’s condition. We believe that this conclusion is unfounded. Perhaps they should have suggested that the combination of ara-C, cidofovir, and antiretroviral therapy had a favorable effect.