[Analysis of five children with acquired thrombotic thrombocytopenic purpura]

Objective: To investigate the clinical characteristics, treatment and prognosis of children with acquired thrombotic thrombocytopenic purpura (TTP). Methods: The clinical manifestations, laboratory examination, treatment and prognosis of 5 children with acquired TTP hospitalized in Beijing Children's Hospital, Capital Medical University from January 2016 to July 2019 were analyzed retrospectively. Results: There were 5 children with acquired TTP including 2 males and 3 females, with the onset age of 8.9(0.8-14.5) years, while 11 children with TTP in the same period. Thrombocytopenia and microangiopathic hemolytic anemia were found in all 5 patients. Only one patient had typical pentalogy of TTP, 3 patients had nervous system symptoms and 3 patients had fever, while renal impairment was relatively rare (1 case). Laboratory examination showed severe thrombocytopenia (7(4-14) ×10⁹/L) and low level of hemoglobin (70(58-100)g/L) in all 5 children. Blood biochemical examination showed that total bilirubin (mainly indirect bilirubin) increased in 3 patients, lactate dehydrogenase increased in 5 patients, and urea nitrogen increased in 1 patient. Bone marrow smear showed megakaryocyte did not decrease. Plasma ADAMTS13 activity was 0 in all 5 patients while ADAMTS13 inhibitor was positive in 4 patients and negative in 1 patient. All 5 children received glucocorticoid therapy, rituximab was added in the early stage of the disease, and 3 children received plasma exchange. The time of platelet recovery to normal was 19 (9-29) days. One child had TTP recurrence after 9 months of treatment. The condition was stable after being treated with glucocorticoid and rituximab again. This case was finally diagnosed as systemic lupus erythematosus after more than 3 years followed up. By December 1, 2020, the follow-up time was 24(16-57) months.The clinical symptoms of all patients disappeared and the platelet level was stable at 159(125-269) ×10⁹/L. Conclusions: Childhood acquired TTP is relatively rare, which can occur in all age groups. The clinical manifestations are mainly thrombocytopenia and microangiopathic hemolytic anemia, the plasma ADAMTS 13 activity and inhibitor test are helpful for the diagnosis of acquired TTP. Plasma exchange and rituximab are effective treatment. This disease requires long-term follow-up.