text: （3）嵌合体型（mosaic）此型约占2%～4%，患者体内具有两种以上细胞系，由于受精卵在早期分裂过程中发生了21号染色体不分离21-三体细胞，形成嵌合体，90%其核型为46，XY（或XX）/47，XY（或XX），+21。
entities.entity: 嵌合体型
entities.label: dis
entities.entity: mosaic
entities.label: dis
entities.entity: 具有两种以上细胞系
entities.label: sym
entities.entity: 21号染色体
entities.label: bod
entities.entity: 受精卵在早期分裂过程中发生了21号染色体不分离
entities.label: sym
entities.entity: 21-三体细胞
entities.label: bod
entities.entity: 嵌合体
entities.label: bod
entities.entity: XY
entities.label: bod
entities.entity: XX
entities.label: bod
entities.entity: XY
entities.label: bod
entities.entity: XX
entities.label: bod