Natural killer cell lymphoproliferative disorder of granular lymphocytes presenting as hemolytic anemia: case report and review of the literature.

Lymphoproliferative disorders of granular lymphocytes (LDGLs) have recently been hypothetically defined based on their immunophenotype, function, and clonality. The majority (129/161) of LDGLs are of the T-cell subset, which is typically associated with neutropenia and occasionally with anemia. The remainder (32/161) are of natural killer cell origin. This subset is associated with neutropenia (52% of cases) and anemia (60% of cases). The anemia most often has no immediately apparent cause. The Coombs test was negative in all cases reported. There is only one reported case of an associated Coombs-negative hemolytic anemia. We report an unusual case of natural killer cell LDGL, defined by morphology and immunophenotypic analysis, presenting as a de novo Coombs-negative hemolytic anemia. The anemia was resistant to steroid therapy. Therapeutic splenectomy resulted in a temporary resolution of the hemolytic process. The splenic pathology is also described.