 Probably the last described kind of diseases are molecular diseases, defined by their molecular characteristics.This was introduced in November 1949, with the seminal paper, "Sickle Cell Anemia, a Molecular Disease", in "Science" magazine, Linus Pauling, Harvey Itano and their collaborators laid the groundwork for establishing the field of molecular medicine.Several classifications of diseases have been historically proposed, and normally all of them assign a code to every supported disease.