BACKGROUND:YKL-40 is a glycoprotein produced by chondrocytes and synovial cells. The plasmatic levels of this metabolite increase in some pathologies such as rheumatoid arthritis and osteoarthrosis, so much so that it can be considered an effective marker of disease activity and in the therapeutic monitoring of these diseases. It has been interesting to dose a group of both male and female subjects affected by seronegative spondylarthritis, comparing this parameter with the disease activity indexes and with the bone turnover markers. METHODS:The study has been carried out on 48 subjects (26 males and 22 females) between 17 and 68 years affected by spondylarthritis, diagnosed in conformity with ARA standards. None of the patients carried out basic treatment or by glycocorticoids, and 22 patients took FANS when required. In these subjects the disease activity markers (VES, PCR, fibrinogen, mucoprotein) and some of the classic bone remodelling markers (blood calcium and phosphates, calciuria, phosphaturia, Ca++, Ntx, osteocalcine, bone isoenzyme of alkaline phosphatase, hydroxyproline, procollagen and YKL-40) were dosed. RESULTS:The comparison between different parameters pointed out that the highest values are obtained in subjects of most advanced age with the highest phlogosis indexes, without any correlation with sex. The quite interesting comparison shows a correlation between the bone remodelling indexes and YKL-40, being particularly remarkable when the disease is more aggressive or during relapse. CONCLUSIONS:It is then possible to confirm that, though preliminary, these data may suggest evaluations on wider case histories to research YKL-40 as a surgical monitoring marker in seronegative poliarthritis.