Coexistence of B-Cell Dyscrasia with Large Granular Lymphocytic Leukemia

Large granular lymphocytic leukemia (LGLL) is an indolent disease and often associated with autoimmune disorders such as rheumatoid arthritis. The association of humoral immune disorders resulting from abnormal B cell activity, may affect original LGLL pathogenesis, clinical presentation and management through modifying disease presentation, progression and/ or resistance to standard care. Coexistence of T cell LGL leukemia with B cell abnormalities has previously been identified in the literature although described in sporadic case reports. However, no large case series or cohorts have been collected so far to study the frequency of the B-cell dyscrasia (BCD) associated with LGLL and describe clinical/ hematological findings in patients with this co-association. Here, we conducted a retrospective review of patients diagnosed with LGL leukemia at The Cleveland Clinic Foundation to search for any associated BCDs. We then classified our population into 2 groups: LGLL with BCD vs. LGLL without BCD, and comprehensively compared them for baseline, clinical and molecular characteristics. A total of 244 T-LGL patients were collected and studied. All cases were uniformly diagnosed with LGLL if 3 out of 4 following criteria were fulfilled, including: 1) LGL count >500/µL in blood for more than 6 months; 2) presence of abnormal CTLs expressing CD3, CD8 and CD57 by flow cytometry; 3) preferential usage of a TCR Vβ family by flow cytometry; 4) TCR gene rearrangement by PCR. Molecular studies including targeted deep sequencing for STAT3mutations were performed. Bone marrow biopsy results were reviewed to exclude other conditions. Endpoints of the study were death or lost to follow up.

In our cohort, we found a frequent manifestation of humoral immune system abnormalities. We identified coexisting BCD in 45% (109/ 244) of LGLL patients, of whom 28 (11.2%) had monoclonal gammopathy of unknown significance (MGUS), and 13 (5.2%) had chronic lymphocytic leukemia (CLL/SLL). Six LGLL patients had multiple myeloma (2.4%). Moreover, polyclonal hypergammaglobulinemia (n=28, 11.2%) or hypogammaglobulinemia (n=14, 5.6%) was reported in 42 LGLL-patients (16.8%). The frequency of other disorders of B-cell origin was also examined. The total incidence of B-cell abnormalities in our LGLL cohort was 45%. Indeed an heterogeneous appearance of other B-cell disorders was observed including mantle cell lymphoma (n=2), DLBCL (n=6), marginal zone lymphoma (n=3), Waldenstrom's macroglobulinemia (n=1), Burkitt's lymphoma (n=1), indolent lymphoma (n=1), Hodgkin's lymphoma (n=1), non-Hodgkin's lymphoma (n=3), neck lymphoma (n=1), and smoldering myeloma (n=2). Patient with LGLL-BCD were older as compared to the ones without (median age: 62 vs. 63 years; ≥60 years: 57% vs. 69%, respectively), although the difference was not statistically significant (P=0.07). Gender was equally distributed (male: 54%, n=132; female: 46%, n=112) in patients who developed BCD. Conventional cytogenetics showed that patients without BCD were more often associated with abnormal cytogenetics (24%, n=9) as compared to LGLL-BCD (9%, n=5). Interestingly, BCD was found in 55 men and 54 women in whom only 6 patients had NK-LGLL while the remaining (n=103 patients) had T-LGLL suggesting a higher association with LGLL of T- rather than of NK-cell origin. Leukopenia was observed in 25/109 patients, with average absolute lymphocytes of 4.18 k/µL and LGL count of 2333 k/µL. Blood count showed: neutropenia in 44, anemia in 65, and thrombocytopenia in 29 out of 109 LGLL patients with BCD. TCR rearrangements were seen in 74 while somatic STAT3 mutations were observed in 37 LGLL patients while more enriched (44%, n=52) in LGLL without BCD. The association of other autoimmune conditions e.g., rheumatoid arthritis, was not different between the two groups (15% vs. 16% in LGLL with BCD vs. without; P=0.8).

In sum, our investigation shows that BCD were frequent in LGLL and coexisted in 45% of the patients, commonly in the form of MGUS, and/ or hypergamaglobulinemia. Perhaps, the co-association of B-cell pathology with LGLL suggests that the two diseases either share pathogenetic driving mechanisms to enhance both B cells and T cells clones or that immunological dysfunction in setting of B cell dyscrasia could trigger/potentiate LGL expansion and/or transformation in this context.