Comparison of 16 non-Portuguese families with MJD from across the world revealed the ACA haplotype in the vast majority, suggesting that this is the ancestral haplotype associated with the affected chromosomes.7 However, the ACA and GGC haplotypes occur with almost equal frequency in expanded chromosomes in the Azores, despite the rarity of the ACA haplotype in the normal population (Table>). In contrast, the ACA haplotype is very common in India, especially in large normal alleles (>26 repeats). This indicates that large normal alleles with the ACA haplotype may have been introduced in the Azores through admixture between the Indian and Portuguese populations, which could have served as founders of the MJD mutation in the Azorean population. This is corroborated by well-documented historical evidence related to the Moorish sea trade and to maritime links between Portugal and South Asia.15 The Portuguese had extensive settlements in India, and though their population was limited, extensive interaction with the local communities was encouraged. By 1815, when the population was formally recorded, there were several families of known mixed descent in Goa and several thousand individuals.16 In addition, slaves were traded from Goa, and a significant number of sailors on Portuguese ships were from the Indian and African coasts. Indian sailors and soldiers were also used extensively in the Portuguese territories further East.15 The maritime importance of the Azores was critical, and soldiers, sailors, and slaves of all regions passed through the islands. Thus, it is reasonable to suggest that a chromosome with the ACA haplotype may have been introduced into Portugal and the Azores by admixture with the South Asian population, and that a subsequent mutation in this haplotype background could have spread worldwide through Portuguese activity. However, this theory needs more careful validation, as maritime links between the Indian subcontinent, Southeast Asia, China, and Africa predate the Portuguese. Data on the ACA haplotype in the normal populations of these regions are not available.