...只在纯合子时才发病，致病基因频率很低，形成纯合状态的机会少，常常只有在近亲婚配时才可能发病，表现为散发病例(sporadic case)，即使是罕见的常染色体显性或X连锁隐性遗传病，也可看到由于新生突变而致的散发病例。
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The situation in Yei is stable and improving daily with the last reported case received on 20 March and only sporadic cases appearing in the town.
耶伊的情况稳定，并且每天都在改善，最后一次报告病例于3月20日收到并且在该镇只出现散在病例。
Isolated case — an individual who is the only member of his or her kindred affected by a genetic disorder, either by chance or by new mutation. See also sporadic.
一个家系中唯一的患病个体，可由上代遗传基因决定，也可由于新突变产生。参见散发。
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