為什麼會天生沒有脾臟?

出生時沒有脾臟既成因可能係遺傳缺陷, 或懷孕期受環境因素影響.
大部分沒有脾臟的人是後天因素, 例如手術切除, 或者因其他病如[鐮刀型紅血球貧血症]等, 令脾臟受破壞痿縮, 終至必須切除.
選譯自維基百科, 原文如下:
Asplenia may rarely be a congenital due to genetic disorders or exposure to environmental factors during gestation. More commonly it is acquired through surgery (splenectomy) or through processes that destroy the spleen, generally through its function to filter the blood and therefore referred to as autosplenectomy (eg spherocytosis and sickle-cell disease).
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由於脾臟最大功能在於免疫=抵抗感染, 沒有脾臟既人比較容易得其他感染既病. 係一個健康既成年人來講, 冇脾臟其實都冇咩所謂, 但嬰兒, 幼童, 老人或長期病患者來講, 冇左脾臟佢既抵抗力會好差, 容易得到[敗血症].