Increased serum level of interleukin-6 in patients with psoriatic arthritis and thrombocytosis.

The role of elevations of serum cytokines in psoriasis is a provocative issue. We report two patients with psoriasis who had episodes of fever, arthritis, and general fatigue. Their symptoms seemed to be associated with increases in serum levels of interleukin (IL)-6, which paralleled the severity of clinical symptoms as well as elevated serum titers of C-reactive protein (CRP) and platelet counts. Since IL-6 is a multipotential cytokine with B-cell activating, T-cell activating, and thrombocytopoietic functions, the symptoms and abnormal laboratory findings in these patients may have been related to their increased serum levels of IL-6. Monitoring the serum level of this cytokine may thus be useful in evaluating the clinical status of patients with psoriatic arthritis.