This variability has led many people to think of it as a spectrum of symptoms rather than a single, clear-cut syndrome. And that variability makes it hard to work out what causes it.

这种多变性令很多人认为它的症状多样而不是单一明确的，这种多样化加大了对其病因的研究难度。

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Because this leads to various diseases, not a single illness, AIDS is referred to as a syndrome.

由于艾滋病会导致多种疾病而不是单一的，因此艾滋病是一种综合症。

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Fragile X syndrome, a single genetic mutation on the X chromosome, is the most common source of inherited mental impairment, affecting one in every 4,000 boys and one in every 6,000 girls.

脆性X综合征，一个X染色体上的基因突变，是遗传性智力障碍最常见的来源，每4000名男孩和每6000名女孩中就有一名儿童患有该症。

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British rock band Muse - who have had the biggest-ever download track with their single Stockholm Syndrome, are also included in the deal.

BBC: NEWS | Entertainment | Festival firm plans download site

There is no cure and not a single proven treatment for SMA. Sometimes known as floppy baby syndrome, it's a leading genetic killer, hitting one in 8, 000 infants and toddlers.

FORBES: For Arya