Background: Many idiopathic thrombotic thrombocytopenia purpura (TTP) patients have severe deficiency of ADAMTS13, an enzyme that cleaves ultralarge von Willebrand multimers. We recently reported that thienopyridine-associated TTP is characterized by an immunologic pathway with severe ADAMTS13 deficiency and a non-immunologic pathway with higher ADAMTS13 activity levels. We now compare findings for idiopathic and thienopyridine-associated TTP patients.

Methods: Clinical findings and laboratory findings were evaluated for 51 idiopathic and 39 thienopyridine-associated TTP.

Results: Clinical findings were similar between idiopathic and thienopyridine-associated TTP for both severe ADAMTS13 deficient and non-deficient patients. Differences were noted in gender and age, relapse rates, and survival.

Conclusion: Among TTP patients with ADAMTS13 deficiency, relapses are frequent in idiopathic TTP patients and Rituximab may be useful, while for thienopyridine-associated TTP patients spontaneous relapse are rare as long as no re-exposure occurs. Among ADAMTS13 non-deficient patients, survival is high following therapeutic plasma exchange (TPE) for idiopathic patients but not for thienopyridine-associated TTP patients. Despite similarities, idiopathic and thienopyridine associated TTP probably have different initiating factors.

ADAMTS13 activity and clinical characteristics in idiopathic and thienopyridine-associated TTP

Idiopathic severe ADAMTS13 deficiency (n=29)†Thienopyridine severe ADAMTS13 deficiency (n=26)Idiopathic non-severe ADAMTS13 deficiency (n=22)†Thienopyridine non-severe ADAMTS13 deficiency (n=13)
*p<0.05 for comparison of severe ADAMTS13 deficiency versus non-severe ADAMTS13 deficiency. †Thienopyridine-associated TTP clinical and presenting neutralizing autoantibody data was summarized from the Journal of the American College of Cardiology publication by Bennett et al. in 2007. ‡Thienopyridine-associated TTP remission autoantibody data was summarized Tsai et al, 2002, Bennett et al, 2000, and Orimo et al, 2002, and included 3 patients. §Data from average of ADAMTS13 deficient and non-deficient cohorts. 
Mean Age 41 67 47 60 
Sex (% female) 79% 54% 86% 39% 
Platelet count/mm3 (mean)* 18,978 9,269 51,409 35,000 
Platelet count <20,000/mm3* 69% 96% 23% 38% 
Hemoglobin (mg/dl; mean) 8.5 8.3 9.0 8.4 
Creatinine (mg/dl; mean)* 1.5 2.2 3.2 3.0 
Creatinine >2.5 mg/dl* 11% 27% 48% 46% 
30-day survival 96% 85% 90% 62% 
Long-term relapse* 42% 8% 0% 0% 
Neutralizing autoantibodies to ADAMTS13 (prior to TPE) § 79% 100% 27% 0% 
Neutralizing autoantibodies to ADAMTS 13 (measured at remission) § 55% 33%‡ 33% 0% 
Idiopathic severe ADAMTS13 deficiency (n=29)†Thienopyridine severe ADAMTS13 deficiency (n=26)Idiopathic non-severe ADAMTS13 deficiency (n=22)†Thienopyridine non-severe ADAMTS13 deficiency (n=13)
*p<0.05 for comparison of severe ADAMTS13 deficiency versus non-severe ADAMTS13 deficiency. †Thienopyridine-associated TTP clinical and presenting neutralizing autoantibody data was summarized from the Journal of the American College of Cardiology publication by Bennett et al. in 2007. ‡Thienopyridine-associated TTP remission autoantibody data was summarized Tsai et al, 2002, Bennett et al, 2000, and Orimo et al, 2002, and included 3 patients. §Data from average of ADAMTS13 deficient and non-deficient cohorts. 
Mean Age 41 67 47 60 
Sex (% female) 79% 54% 86% 39% 
Platelet count/mm3 (mean)* 18,978 9,269 51,409 35,000 
Platelet count <20,000/mm3* 69% 96% 23% 38% 
Hemoglobin (mg/dl; mean) 8.5 8.3 9.0 8.4 
Creatinine (mg/dl; mean)* 1.5 2.2 3.2 3.0 
Creatinine >2.5 mg/dl* 11% 27% 48% 46% 
30-day survival 96% 85% 90% 62% 
Long-term relapse* 42% 8% 0% 0% 
Neutralizing autoantibodies to ADAMTS13 (prior to TPE) § 79% 100% 27% 0% 
Neutralizing autoantibodies to ADAMTS 13 (measured at remission) § 55% 33%‡ 33% 0% 
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Topics:
thienopyridine, thrombotic thrombocytopenic purpura, epidemiology, surveillance, medical, autoantibodies, creatinine, disease remission, tropical eosinophilia, adamts proteins, enzymes

Disclosures: No relevant conflicts of interest to declare.

Author notes

Corresponding author

2008, The American Society of Hematology
2008
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