HeredityGeneticsElephantiasisDiseases in TwinsHistory, 19th CenturyTwins, MonozygoticTwins, DizygoticSwedenEnvironmentGenes, RecessiveGenetic Predisposition to DiseasePhenotypeRisk FactorsFamily HealthPedigreeGenes, DominantGenetic LinkageSex FactorsBiological EvolutionGenetic VariationAge FactorsPolymorphism, Single NucleotideGenotypePrevalenceQuestionnairesCohort Studies