| 著者 |
近藤, 明宏
瀬尾, 佳代子
竹内, 彰浩
森, 亮輔
西谷, 真里
八木, 弘文
木内, 洋之
Seo, Kayoko
Takeuchi, Akihiro
Mori, Ryosuke
Nishitani, Mari
Yagi, Hirofumi
Kiuchi, Hiroyuki
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内容記述 |
非Down症児における急性巨核芽球性白血病 (AMKL) の発症は稀であり, 予後不良である.
症例は1歳4ヶ月の女児. 繰り返す発熱を主訴に他院にて治療されていたが, 末梢血中に芽球が出現したため, 香川大学医学部附属病院小児科に紹介入院となった. 血液検査の結果, 著明な白血球増多と貧血を呈しており, 芽球を2.0%認めたことから, 白血病の可能性を考慮し, 骨髄検査が行われた. 骨髄は高度過形成で芽球様細胞が78.8%認められた. 芽球様細胞は大小不同があり, 細胞質は好塩基性が強く, 辺縁はときにbleb様突起などの不整があり, ミエロペルオキシダーゼ (MPO) 染色は陰性であった. フローサイトメトリー (FCM) による細胞表面抗原はCD33, CD56, CD61, CD117陽性で, CD9, CD34, CD36, CD41, CD110などは陰性を示し, 細胞質内抗原ではTdT, CD3, CD79a, MPOがいずれも陰性であった. FCMの結果からAMKLの可能性を疑い, 細胞質内のCD41とCD61を追加で染色したところ共に陽性を示した. さらに染色体検査の結果が正常女性核型であったことから, 上記の所見と合わせて小児非Down症AMKL (non-DS-AMKL) と診断された.
AMKLの巨核芽球は血小板関連抗原 (CD41, CD61, CD42b) のうち一つ以上が陽性を示すとされる. 本症例は形態的にAMKLの特徴を一部有し, 細胞表面のCD61が陽性でAMKLの条件を満たしたが, 非Down症児であることから, 芽球に付着した血小板による偽陽性の可能性を否定できず診断に苦慮した. しかし, 特異性が高いとされる細胞質内CD41, CD61の発現を証明できたことが確定診断をする上で根拠の一つとなり, FCMによる細胞内染色の重要性を再認識した症例であった.
Acute megakaryoblastic leukemia (AMKL) in children without Down syndrome is rare and has a poor prognosis.
A 16-month-old female, who was treated at another hospital with repeated fever, was referred to the Department of Pediatrics, Kagawa University Hospital, because of the appearance of blast cells in peripheral blood. A blood test showed marked leukocytosis and anemia, with 2.0% blast cells. Bone marrow was markedly hypercellular and 78.8% blast cells were observed. Blast cells were uneven in size, the cytoplasm was strongly basophilic, and the margins were sometimes irregular with bleb-like processes, and myeloperoxidase (MPO) staining was negative. Cell surface antigens by flow cytometry (FCM) were positive for CD33, CD56, CD61, and CD117, and negative for CD9, CD34, CD36, CD41, and CD110. The cytoplasmic antigens were negative for TdT, CD3, CD79a, and MPO. We suspected AMKL from FCM results, and when cytoplasmic CD41 and CD61 were additionally stained, both were positive. Furthermore, because the result of the chromosomal test showed a normal female karyotype, together with the above findings, a diagnosis of pediatric AMKL without Down syndrome (non-DS-AMKL) was made.
AMKL megakaryoblasts are said to be positive for one or more of the platelet-related antigens (CD41, CD61, CD42b). This case had some morphological characteristics of AMKL, and the cells were positive for sCD61 which satisfied the conditions for AMKL. But because she was a non-Down syndrome child, the possibility of false positives due to platelets attached to blast cells could not be ruled out, making diagnosis difficult. However, the expression of cyCD41 and cyCD61, which are considered to be highly specific, was one of the criteria for making a definitive diagnosis. This case reaffirms the importance of intracellular staining by FCM. |
AA12468526_13_051 (9.3 MB)
