48,XXXX syndrome human tetrasomy tetrasomy X http://purl.bioontology.org/ontology/MESH/C536502 https://en.wikipedia.org/wiki/Tetrasomy_X https://www.wikidata.org/wiki/Q2758894 48 XXXX 48,XXXX The possession of four copies of the X chromosome in an otherwise diploid cell, making the person's karyotype 48,XXXX. quadruple X tetra X tetrasomy of chromosome X tetrasomy of the X chromosome tetrasomy type X