染色体22q11.2欠失症候群患者における非定型多糖カプセルを有する肺炎球菌血清型10Aによる致死的圧迫性脾臓摘出後感染症。症例報告

Fatal overwhelming postsplenectomy infection due to Streptococcus pneumoniae serotype 10A with atypical polysaccharide capsule in a patient with chromosome 22q11.2 deletion syndrome: A case report.

• Keiko Matsuoka
• Itaru Yanagihara
• Yukiko Kawazu
• Maho Sato
• Masahiro Nakayama
• Yukiko Nakura
• Nao Kanagawa
• Yukihiro Akeda
• Futoshi Fujiwara
• Kazutoshi Itoh
• Hiroaki Kawata
• Makoto Takeuchi

抄録

肺炎球菌ワクチンで適切な予防を行ったにもかかわらず，肺炎球菌による肺炎球菌感染症（OPSI）で死亡した22q11.2染色体欠失症候群の10代患者の初症例を報告する．先天性心疾患を有しており、いくつかの手術を受けた。免疫不全は臨床的には認められなかった．死亡の2年前に薬剤耐性特発性血小板減少性紫斑病で脾臓摘出術を行い，脾臓摘出術の4ヵ月後に23価肺炎球菌多糖類ワクチン（PPV23）を接種した．軽度のインフルエンザ様症状を呈して急死した。剖検が行われ，OPSIと診断された．血液培養ではS.pneumoniaeが陽性であった．この分離されたS.pneumoniaeは多価血清凝集検査では血清型別できなかった．逆に，多座配列タイピング後のDNA配列決定により，10A型であることが示唆された．また，一価および因子特異的血清を用いた追加検査により，本菌は10A型であることが確認された．また，本菌の超微細構造を観察したところ，多糖類カプセルは薄く，まばらであった。このカプセルの形態異常が多弁性血清凝集不全の原因であり，この症例で観察されたOPSIの重症度と関連している可能性が示唆された．染色体22q11.2欠失症候群は、特定の免疫不全症、特にS.pneumoniae感染症に罹患しやすい疾患と関連しているが、致死的なOPSIは報告されていない。免疫不全のリスクがあるこれらの患者には、ワクチン接種に加えて、予防的な抗生物質の投与が必要かもしれません。

We report the first case of a teenage patient with chromosome 22q11.2 deletion syndrome who died of overwhelming postsplenectomy infection (OPSI) by Streptococcus pneumoniae despite appropriate prevention by pneumococcal vaccine. He had congenital heart disease and underwent several surgeries. Immunodeficiency had not been noticed clinically. Two years prior to death, splenectomy was performed for a drug-resistant idiopathic thrombocytopenic purpura and he was immunized with 23-valent pneumococcal polysaccharide vaccine (PPV23) 4 months after splenectomy. He died suddenly after a mild flu-like symptom. Autopsy was performed and OPSI was diagnosed. Blood culture was positive for S. pneumoniae. This isolated S. pneumoniae strain was serotypically un-typable by polyvalent serum agglutination test. On the contrary, multilocus sequence typing followed by DNA sequencing indicated the molecular serotype as 10A. Additional testing using monovalent and factor-specific sera confirmed the strain as serotype 10A. Ultrastructural observation of this S. pneumoniae strain showed that the polysaccharide capsule was thin and sparse. We speculate that the abnormal morphology of the capsule may have accounted for the polyvalent serum agglutination failure and may possibly be associated with severity of OPSI observed in this case. Chromosome 22q11.2 deletion syndrome is associated with certain immunodeficiency, especially susceptible to S. pneumoniae infections; however, fatal OPSI has not been reported. In addition to vaccination, prophylactic antibiotics may be necessary for these patients who are at risk of immunodeficiency.

Copyright © 2018 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.