Taking into account the presence of galectin-3 in immune cells, and the role of immune system in rheumatic diseases the purpose of our study was to assess the serum galectin-3 concentration and compare its diagnostic values with the routinely used tests between rheumatic diseases, including rheumatoid arthritis, systemic sclerosis, and systemic lupus erythematosus. The gene discussed is LGALS3; the disease is rheumatoid arthritis.