RESUMO
The HLA allele frequency distribution of the Mayans from Guatemala was studied and compared with those of other First American Natives and worldwide populations (a total of 12,364 chromosomes and 6182 individuals from 60 different populations). The main conclusions were (1): the closest Amerindian group to Mayans is the Arhuacs, who were the first recorded Caribbean Islands' inhabitants (2). Mayans are not so close to Mesoamerican Zapotec, Mixe and Mixtec Amerindians, who genetically cluster together. Mixe had been related to Mayans only on linguistic bases (3). DRB1*0407 and DRB1*0802 alleles are found in 50% of Mayans; these alleles are also found in other Amerindians, but the Mayans' high frequencies may be showing a founder effect for this Mesoamerican-Caribbean population (4). Extended Mayan specific HLA haplotypes are described for the first time (5). Language and genes do not completely correlate in microgeographical studies (6). Significant genetic input from outside is not noticed in Meso and South American Amerindians according to the genetic analyses; while all world populations (including Africans, Europeans, Asians, Australians, Polynesians, North American Na-Dene Indians and Eskimos) are genetically related. Meso and South American Amerindians tend to remain isolated in the neighbour joining analyses.
Assuntos
Etnicidade/genética , Antígenos HLA/genética , Indígenas Centro-Americanos/genética , Alelos , Efeito Fundador , Frequência do Gene , Genética Populacional , Guatemala , Antígenos HLA-B/genética , Antígenos HLA-DR/genética , Haplótipos , Humanos , Desequilíbrio de Ligação , Análise de Sequência de DNARESUMO
The name epidermal nevus syndrome could be applied to a group of clinically and histopathologically different entities as has been pointed out by Happle. Phacomatosis pigmentokeratotica is a further type of epidermal nevus syndrome distinguished by the presence of a sebaceous nevus and a contralateral speckled lentiginous nevus of the papular type, associated with skeletal or neurological abnormalities. Three new cases of this recently delineated syndrome are presented. A common origin may account for the temporal and spatial relationship between the epidermal and the speckled lentiginous nevus. The concept of melanocytic-epidermal twin spotting similar to the interpretation of vascular twin spotting could explain the pathogenesis of this entity.