Rituximabとvincristineの併用が奏効した難治性血栓性血小板減少性紫斑病 Refractory thrombotic thrombocytopenic purpura successfully treated with a combination of rituximab and vincristine

症例は26歳男性。2006年1月1日，嘔吐，発熱があり救急車で来院。見当識障害，点状出血，ヘモグロビン尿，微小血管障害性溶血性貧血，血小板数減少（1.4万/μl）を認め，Thrombotic thrombocytopenic purpura (TTP)と診断した。ステロイドパルスと連日の血漿交換で血小板数は数日間増加したがすぐに1.0万/μl以下となった。血漿交換を継続しつつrituximabとvincristineを投与したところ血小板数は速やかに正常化した。von Willebrand因子切断酵素(ADAMTS13)活性とそのインヒビターの力価は血小板数と相関しており定型的な後天性TTPであった。血漿交換不応の難治性TTPにrituximabとvincristineの併用が奏効した一例を報告する。

A 26-year-old man was referred to our hospital with vomiting and high fever. He was disoriented and laboratory results showed microangiopathic hemolytic anemia (Hb 7.1 g/d<i>l</i>) and severe thrombocytopenia (15×10³/μ<i>l</i>). The diagnosis of thrombotic thrombocytopenic purpura (TTP) was established. The activity of von Willebrand cleaving protease (ADAMTS13) was found to be remarkably low (<0.5%) and the high activity of the inhibitor (11.0 Bethesda U/m<i>l</i>) was detected, confirming the diagnosis of typical acquired TTP. Although he had been successfully treated with daily plasma exchange and methylprednisolone, he relapsed after a week. To this therapeutic strategy we added four weekly doses of rituximab (375 mg/m²) and two weekly doses of vincristine (1 mg/m²) simultaneously. The response was very rapid and complete, that is, the platelet count recovered to normal seven days after the first rituximab and vincristine treatment. The patient maintains complete remission nine months later under the administration of 17.5 mg prednisolone. Recovery of the plasma ADAMTS13 activity was clearly correlated with the decrease or disappearance of the inhibitor activity. Combination of rituximab and vincristine therapy would appear to be very effective against refractory TTP.