Are Patients Who Have Recovered From ADAMTS13-Deficient Thrombotic Thrombocytopenia Purpura (TTP) at Risk for Developing Systemic Lupus Erythematosus (SLE)?

Abstract 2519

TTP associated with acquired, ADAMTS13-deficiency and SLE are both autoimmune disorders that occur preferentially in young, black women and they have many similar clinical features. TTP may occur in patients previously diagnosed with SLE, or patients may develop SLE following recovery from TTP. In addition, TTP may be quite difficult to distinguish from SLE patients with severe hematologic manifestations. We compared the prevalence of SLE-associated autoantibodies in TTP patients to published population data using 95% confidence intervals (CI). The Oklahoma TTP Registry enrolled 292 consecutive patients with their first episode of clinically diagnosed TTP from 11–13-1995 (date of our initial ADAMTS13 measurement) to 7–31-2009; ADAMTS13 activity was measured in 271 (93%) patients; 64 (24%) patients had ADAMTS13 activity <10%, 63 were evaluated for SLE-associated autoantibodies, including 2 patients with a previous diagnosis of SLE. Serum from the patient's acute initial episode was used for analysis. The prevalence of ANA, anti-dsDNA, anti-Ro, and aPL in TTP patients was significantly higher than published population data; prevalences of anti-nRNP, anti-Sm, and anti-La were not different.

Because of the increased prevalence of SLE-associated autoantibodies, we evaluated our TTP patients for the America College of Rheumatology (ACR) criteria for SLE (presence of ≥4 of 11 criteria suggests the diagnosis of lupus); abnormalities associated with any TTP episode were not counted in this evaluation of clinical criteria for SLE. By definition ACR criteria can be fulfilled serially or simultaneously over a lifetime. Evaluations were completed between 6-1-2007 and 5-1-2009 on 38/42 (90%) eligible patients (alive, non-institutionalized, no previous SLE diagnosis) consisting of physical examination, review of available lifetime medical records, and serial laboratory evaluations. Patients have been followed for a median of 8.3 years (range, 1–14 years). During this time, 3 (8%) developed clinically evident SLE requiring treatment 1, 5, and 70 months after their initial TTP episodes. Among the other 35 patients, 3 (8%) have ≥4 SLE classification criteria by medical record review (1 had pre-existing Sjögren's syndrome and receives treatment; 2 have minimal clinical features and are not actively treated for SLE); 9 (24%) have 3 criteria; 16 (42%) have 2 criteria; 6 (16%) have 1 criterion; and 1 (2%) patient has no ACR criteria for SLE. All patients continue to be followed and clinically evaluated for potential intervention. SLE diagnosis is a clinical designation and because of the lack of disease modifying drugs, routine follow-up is standard of care unless the patient is symptomatic.