Acquired, noncongenital thrombotic thrombocytopenic purpura in children and adolescents: clinical management and the use of ADAMTS 13 assays.

Thrombotic thrombocytopenic purpura (TTP) in children is rare and is often thought to be due to congenital ADAMTS13 deficiency. We report seven new cases of noncongenital TTP in children and adolescents and perform a review of the literature where ADAMTS13 assays have been performed in paediatric acquired TTP. All new cases were female and the median age was 13 years. Presenting clinical features included bruising/petechiae or bleeding, fever, neurological, and renal impairment. Median Hb and platelet counts on admission were 66 g/l and 10 x 10(9)/l respectively. Two cases had raised Troponin T levels and one had an abnormal ECG. All cases had ADAMTS13 activity less than 5% and an inhibitor to ADAMTS13. The median number of plasma exchange to remission was 22.5. Six cases received rituximab. Three achieved normal ADAMTS13 activity and remain in remission. Two had persistently low ADAMTS13 activity with high anti-ADAMTS13 IgG levels and one of these relapsed. One had moderately reduced levels of ADAMTS13 in remission with no inhibitor, however, a fall in ADAMTS13 activity and increase in anti-ADAMTS13 IgG heralded clinical relapse. The literature review identified 12 acquired cases showing low ADAMTS13 activity and inhibition of ADAMTS13 (in 95%). In children and adolescents TTP may be due to acquired deficiency of ADAMTS13, associated with an inhibitor/Anti-ADAMTS13 IgG antibodies. Treatment of acquired disease requires PEX and usually immunosuppressive treatment. Rituximab appears to be an effective adjunctive treatment modality.