A fatal disseminated cryptococcal infection in a patient treated with zanubrutinib for Waldenström's macroglobulinemia.

We report herein a case of fatal disseminated cryptococcosis in the setting of zanubrutinib use for Waldenström's macroglobulinemia. At the time of diagnosis, his Waldenström's macroglobulinemia was in a partial response. The mechanism by which Bruton tyrosine kinase inhibitors (BTKs) lead to invasive fungal infections in these patients remains to be explored. T- and B-cell immune defects accompanying low-grade B-cell lymphomas may contribute to the severity of these infections.