T Cell Large Granular Lymphocytic Leukemia and Co-Existing Plasma Cell Disorders
Authors: Sidiqi M Hasib , Aljama Mohammed A , Viswanatha David S. , Dingli David 
Published: October 2019

Abstract
T cell large granular lymphocytic (T-LGL) leukemia has been reported to occur in patients with plasma cell disorders (PCD). We conducted a retrospective review of patients diagnosed with T-LGL leukemia and a PCD at the Mayo Clinic.
22 patients were identified with T-LGL leukemia and a plasma cell disorder. The T-LGL leukemia preceded the PCD in 18% (n=4), was synchronous in 50% (n=11) and diagnosed post plasma cell disorder in 32% (n=7) of patients. The PCD diagnosis varied and included monoclonal gammopathy of undetermined significance (MGUS, n=13), multiple myeloma (MM, n=5), smoldering multiple myeloma (SMM. N=2), lymphoplasmacytic lymphoma (LPL, n=1) and monoclonal gammopathy of renal significance (MGRS, n=1). 5 patients developed T-LGL leukemia after treatment for a PCD (4 with MM and 1 with LPL). 4 patients with MGUS progressed to a more aggressive disease, 3 to MM and 1 to LPL. Neutropenia (76%) and anemia (70%) were the most common clinical presentation. None of the patients had rheumatoid arthritis. Treatment for the TLGL was variable with a number of different agents used listed in Table 1. 45% (n=10) of patients had an indolent course and did not receive specific therapy for TLGL. 6 patients responded to a single line of therapy, all of whom received either cyclophosphamide or methotrexate based regimens. The remainder had a relapsing course with multiple lines of therapy including 2 patients that received splenectomy.
Nine patients were identified as having symptomatic multiple myeloma and TLGL, Table 2. Four patients had progressed from a preexisting plasma cell disorder, 3 with MGUS and 1 with SMM. The diagnosis of TLGL preceded myeloma in 1 patient was concurrent in 4 and post myeloma diagnosis in 4 patients. Time to diagnosis of TLGL post myeloma ranged from 10 to 63 months. At time of LGL diagnosis neutropenia was present in 7/9 patients and anemia in 6/8 (data unavailable for 1 patient). Cytogenetics data was available in 7 patients. Hyperdiploidy was the most common abnormality (3/7) followed by deletion 13q (2/7), t(14;16) in 1 patient and 1q amplification in 1 patient. The majority of patients were treated with novel agents with 7 receiving bortezomib based therapy. 3 patients underwent autologous stem cell transplantation. Therapy directed at the TLGL was given to 4/9 patients. This consisted of a combination of cyclophosphamide and prednisone in 3/4 patients all of whom responded to therapy with resolution of cytopenias. One patient had TLGL with multiple relapses and required multiple lines of therapy including eventual splenectomy. 3 patients with TLGL diagnosed after the diagnosis of myeloma did not receive specific therapy directed at the TLGL. The clinical course of the TLGL in these 3 patients was indolent and did not appear to be affected by therapy for multiple myeloma.
At last follow up 5 patients have died. After a median follow up of 76 months post TLGL diagnosis the median overall survival (OS) post TLGL diagnosis was not reached for the entire cohort. In the cohort of patients with multiple myeloma, median OS from time of myeloma diagnosis was 71 months. Median OS from time of TLGL diagnosis was not reached.
T-LGL leukemia can present in patients with a variety of plasma cell disorders and occur at any stage of the disease process. It is an important differential to consider in patients with unexplained cytopenias that are incongruent with the activity of the plasma cell disorder.

Disclosures
Dingli: Millennium Takeda: Research Funding; Alexion Pharmaceuticals, Inc.: Other: Participates in the International PNH Registry (for Mayo Clinic, Rochester) for Alexion Pharmaceuticals, Inc.; Alexion Pharmaceuticals, Inc.: Other: Participates in the International PNH Registry (for Mayo Clinic, Rochester) for Alexion Pharmaceuticals, Inc.; Millennium Takeda: Research Funding.