title: Twin studies: genetic factors are important.
authors: S R
authors: SR
authors: Block
mesh_terms: D004200:Diseases in Twins / Q000235:genetics*; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic