ENAs originally referred to proteins found in a saline extract of cell nuclei. Its components have since been more clearly identified and in fact include many cytoplasmic molecules. The misnomer however has stuck. These proteins are intimately associated with various RNA molecules and are thus called ribonucleoproteins, but the nomenclature used for them is often a source of confusion, Sm, Ro and La were named after the first 2 letters of the surnames of the patients in whom they were first found. Two proteins associated with Sjogren's Syndrome were independently described as antigens A and B, but are now known to be identical to Ro and La respectively. i.e. SS-A = Ro and SS-B = La.