Atypical lymphoproliferative disorder in a patient with X-linked thrombocytopenia

Is there a (host) genetic predisposition to progressive multifocal leukoencephalopathy?

Progressive multifocal leukoencephalopathy (PML) has been described in association with a variety of predisposing risk factors, including HIV/AIDS, lymphoproliferative disorders and, most recently, treatment with a range of biologics, most notably natalizumab in multiple sclerosis (MS) (1). However, while these underlying disorders appear to be (usually) necessary, they are not sufficient to predict the development of PML, since only a small fraction of such individuals will succumb, raising the question of whether host genetic factors must also play a role. Evidence is mounting that this is, indeed, the case but more work needs to be done to fully delineate these underlying genetic factors. Finally, while it is possible that an underlying genetic susceptibility for PML in general will be uncovered in the future, the current evidence argues for a collection of multiple, individually rare underlying susceptibilities (with one predominant single genetic susceptibility in each individual), as described in this review.

Hematopoietic Stem Cell Transplantation for X-Linked Thrombocytopenia With Mutations in the WAS gene

X-linked thrombocytopenia (XLT) is a mild form of the Wiskott-Aldrich syndrome (WAS) caused by mutations in the WAS gene. A recent retrospective study of the clinical outcome and molecular basis of a large cohort of XLT patients demonstrated that although overall survival is excellent, event free survival is severely affected with conservative treatment. To answer the question whether hematopoietic stem cell transplantation (HSCT) offers a viable alternative therapeutic option in XLT, we retrospectively investigated the outcome of HSCT in a cohort of 24 XLT patients who received HSCT between 1990 and 2011 at 14 transplant centers in the United States, Italy, Germany, Canada, and Japan. The engraftment rate was 100% and the overall survival rate was 83.3%. Of the four non-survivors, 2 underwent splenectomy prior to HSCT and died of sepsis, and two of aspergillus infections associated with severe GVHD. In all but one patient, pretransplant complications were resolved by HSCT. Our data indicate that HSCT following myeloablative conditioning is curative and associated with acceptable risks as a treatment option for XLT.