6590 Background: The purpose of this study is to analyze patients enrolled in the LGL leukemia registry to distinguish the similarities between LGL leukemia and rheumatoid arthritis in order to access overlapping immune mechanisms that may be responsible for neutrophil mediated destruction. Methods: A retrospective chart review was performed on 79 patients enrolled in the LGL registry at Penn State Cancer Institute. All patients enrolled in the study had a diagnosis of both rheumatoid arthritis and potentially LGL leukemia. Data was collected for age, sex, RF factor positivity, family history, autoimmune disease, T-cell receptor gene rearrangement, and bone marrow invasion. Results: Of 79 patients the mean age of onset for LGL leukemia was 60 years old with no discrepancy noted between sexes, 37 M, 42 F. 49 patients were positive for rheumatoid factor. 27 patients had rheumatoid arthritis in a first degree relative with no discrimination between maternal or paternal inheritance. 22 patients were positive for any other autoimmune process. 60 patients were positive for T-cell receptor gene rearrangement. Of the remaining 19 patients that were negative for T-cell receptor rearrangement, 12 had evidence of bone marrow invasion (CD3/CD8+ infiltrate in >20% bone marrow) and two showed bone marrow invasion of NK cell LGL (CD3/CD8-, CD57+) (Table). Conclusions: Patients with T cell LGL leukemia and rheumatoid arthritis appear to be clinically similar with regard to age, duration of disease, and other autoimmune disorders as patients with rheumatoid arthritis alone. Our patient population showed those with TLGL and RA also tends to have a positive family history of RA in up to 20% as opposed to 5-10% in RA patients. Given that RA and TLGL have a significantly higher expression of the HLA-DR4 haplotype than healthy patients, it is conceivable that with shared genetic alterations, and gene environment interactions that may promote posttranslational modification, there may be a loss of tolerance resulting in T cell activation, and eventual transformation into a T cell clone. [Table: see text]
