Characteristics of progressive multifocal leukoencephalopathy in hematological malignancies, With reference to HIV-infected patients.

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic infection of the central nervous system (CNS) observed in immunocompromised individuals. We retrospectively evaluated the clinical courses of PML in patients with hematological malignancies at North Japan Hematology Study Group institutions, using patients with human immunodeficiency virus (HIV) infection as a reference. Eight PML patients had hematological malignancies and 9 had HIV infection. CD4 + T cell counts were markedly low in patients with hematological malignancies (median 168/μl, range 48.4-330/μl) and did not differ significantly from those in patients with HIV infection (median 28/μl, range 8-225.4/μl). IgG levels were significantly lower in patients with hematological malignancies (median 643.5 mg/dL, range 205-2478 mg/dL) than in patients with with HIV infection (median 1691.5 mg/dL, range 1304-3014 mg/dL) (p < 0.01). Almost all patients with hematological malignancies died after progression of PML (median time from onset to death, 136 days). In contrast, seven patients with HIV infection were alive at the end of follow-up. The incidence of PML in patients with hematological malignancies may increase with the introduction of new antibody drugs and cellular therapies in future. Considering the poor prognosis, greater caution is warranted regarding this serious complication.