Intravenous Immunoglobulin Is an Effective Treatment for LGL-Mediated Immune Cytopenias in Myelodysplastic Syndromes and Other Bone Marrow Failure Syndromes

Background: Myelodysplastic Syndrome (MDS) and Aplastic Anemia (AA) are often associated with clinical immune manifestations. An abnormal profile of the T-cell repertoire can be detected in these patients (pts) and is thought to play a role in bone marrow (BM) insufficiency. The presence of a co-existent large granular lymphocytic (LGL) clone may exacerbate cytopenias independent of the primary disease mechanism and offers another target for therapeutic intervention. Treatment for LGL proliferation is usually immunosuppressive therapy but there is no accepted standard of care.

Methods: We explored the role of intravenous immunoglobulin (IVIG) as a treatment for immune-related cytopenias, i.e. Coombs negative (C-) hemolytic anemia, in a series of 12 consecutive pts with an LGL clonal proliferation documented by flow cytometry and TCR clonal rearrangements. Of the 12 cases, 9 had MDS (7 lower-risk), 1 AA with LGL liver involvement, and 1 primary myelofibrosis. One patient (pt) had suspected MDS. Overall response was assessed by MDS IWG criteria 2006. We defined a hemolysis response (HLR) as complete normalization (CR) or, a greater than 50% improvement (PR) in deviation from normal values of LDH, reticulocytes, indirect bilirubin and haptoglobin. Duration of HLR was defined as the time from onset of HLR to the time of resumption of hemolysis and loss of effect of IVIG.

Results: All pts were treated with IVIG administered at a dose of 500mg/kg of IVIG once per week, in repeated cycles, with a duration ranging from 1-4 week(s) per cycle. Clinical characteristics (Table 1): M/F ratio 10/2; median age 69. Ten pts had a CD3+ T-LGL and 2 had a CD3-/CD16+/CD56+ NK-LGL circulating clone. Karyotype abnormalities were non-specific; 8 pts had 1-3+ reticulin BM fibrosis; 4 had mutations in RNA-splicing genes: SF3B1 (2); SETBP1 (1); SRSF2 (1). Ten pts were evaluable for response: 8 pts responded (ORR 80%): Hematological improvement (HI-erythroid) 8/8 (100%); a hemolysis CR (HLR-CR) occurred in 7 (87.5%) and hemolysis PR (HLR-PR) in 1 pt (12.5%). Median number of cycles, follow up, and duration of treatment were 16, 21.5 and 9.5 months (mo), respectively. The HLR-CR was durable and prolonged in 3/8 (38%) pts; 2 of these 3 pts (67%) did not require maintenance IVIG. Relapse from HLR occurred in 4, during infection or chemotherapy, but the response returned to the original level by shortening the intervals between administration of IVIG. One pt had relapsed after an initial response and then became refractory to IVIG. In follow up at month 38, 75% of pts were still responding to treatment, and 1 pt was still in remission after 46 mo. In 4 of 6 pts, corticosteroid treatment was discontinued and no longer required for chronic hemolysis, with general improvement of steroid related symptoms. Some patients had been on steroids maintenance for periods ranging from months to years. Response was more durable with continuous rather than sporadic dosing. Adverse events were not specific: 1 pt with self-limited isolated palpitations; 1 pt with hypertension not requiring intervention.

Conclusions: Treatment with IVIG of immune cytopenias associated with LGL clones and BMF yields durable responses in 80% of pts. IVIG, especially at high concentrations, may enhance apoptosis, suppress proliferation of T-cells and induce immune-regulation. Given the relative rarity of LGL clones in MDS, further investigational studies will help define the role of IVIG and clarify the mechanism of action in this group of pts with MDS and BMF associated with LGL clones.