HeredityGeneticsElephantiasisDiseases in TwinsHistory, 19th CenturyTwins, MonozygoticTwins, DizygoticSwedenEnvironmentGenes, RecessiveGenetic Predisposition to DiseaseRisk FactorsFamily HealthPhenotypePedigreeGenes, DominantGenetic LinkageSex FactorsAge FactorsBiological EvolutionGenetic VariationPolymorphism, Single NucleotidePrevalenceGenotypeQuestionnairesCohort Studies