Subcutaneous (sc) Anti-D Treatment of Childhood Idiopathic Thrombocytopenic Purpura (ITP).
Authors: Kjaersgaard Mimi , Edslev Pernille W. , Hasle Henrik 
Published: October 2019

Abstract
Purpose: To investigate the platelet enhancing effect of sc anti-D in children with ITP.
Material and methods: We included 21 children admitted to a pediatric department in Denmark with ITP, platelet (PLT) count < 30 · 109/L, rhesus D positive blood type, hemoglobin >10 g/dL, normal creatinine, and bleeding not requiring immediate intervention, i.e. grade 1–3 on Buchanan and Adix six-step-scale. Fourteen children had acute ITP (aITP) and seven chronic ITP (cITP). All patients were treated with sc anti-D 50 μg/kg.
Results: Two children with aITP were treated with intravenous IgG (IVIG) prior to sc anti-D. Six of seven cITP children had received IVIG treatment. The IVIG was repeated monthly, or with shorter intervals, in five of six children up to six months after diagnosis, with declining effect on PLT count. The figure illustrats the time courses of PLT count, hemoglobin (Hgb), lactate dehydrogenase (LDH), and reticulocyte count. The median bleeding score was 1 and mean PLT count 9 · 109/L at time of treatment = day 0. Three days after treatment = day 3, the mean PLT count was significantly increased to 36 · 109/L (t-test p=0.005). Among 17 children with a PLT count <10 · 109/L day 0, 41% had a PLT count of at least 20 · 109/L day 3 and 71% day 6. A PLT count >50 · 109/L was reached day 6 in 43% and in 62% day 12. Children with aITP: The PLT count ranged from 1–15 · 109/L (mean 7 · 109/L) day 0 and had increased in 10 of 13 children by day 3. However, in two children the PLT count remained below 10 · 109/L. Two children received a second anti-D dose day 3. Before day 6, the PLT count had increased in three additional children. The mean PLT count increased from 7 · 109/L to 30 · 109/L day 3 (t-test p=0.04). At last control visit between 2–12 months after treatment, six of the children had had normal PLT counts for at least three months without further medical treatment. Children with cITP: The PLT count was 2–41 · 109/L (mean 15 · 109/L) day 0, and the mean PLT count increased to 52 · 109/L day 3 (t-test p=0.01). An increase in PLT count to >20 · 109/L was achieved in five children day 3 and in six day 6. Four children had a PLT count increase to >50 · 109/L day 3. Four of the cITP children experienced a PLT count decrease to <30 · 109/L 10–49 days after sc anti-D. Three of the four children were treated repeatedly with sc anti-D, with an effect comparable to the first treatment. All seven children were thrombocytopenic at last control visit 1–6 years after treatment. Two children experienced mild fever and chills within 24 hours of treatment. Pain at the injection site was common but tolerable and brief. In two children Hgb decreased >2.0 g/dL (2.3 g/dL and 2.7 g/dL). No children wewe transfused. Median Hgb decline was 0.72 g/dL (Wilcoxon p=0.04). In children with acute ITP Hgb significantly decreased, LDH remained unchanged, and reticulocyte count significantly increased. Hgb decreased from 11.6 g/dL at treatment to 10.5 g/dL day 6 (t-test=0.03, n=11). Mean reticulocyte count increased from 66 · 109/L day 0 to 132 · 109/L day 6. In children with cITP no significant changes was observed in Hgb, LDH or reticulocyte count.
Conclusion: A single dose of sc anti-D 50 μg/kg may be an effective and well-tolerated treatment option in childhood ITP.
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