Some clusters of it are found only in the Dominican Republic and a few other countries, where, in relatively isolated communities, many people are related to each other.

• 只有在多米尼加共和国和其他一些国家才发现有群发病案，在那些与外界相对隔绝的国家里，他们中许多人相互通婚，(因而将疾病遗传给下一代)。