Synchronous fluctuation of interleukin-6 and platelet count in cyclic thrombocytopenia and thrombocytosis.

We describe a case of cyclic thrombocytopenia and thrombocytosis, whose cytokine levels, granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-6 (IL-6) in plasma, fluctuated in synchrony with platelet count. The levels of the two cytokines correlated significantly with the platelet count for 11 observations over an 8-month period (r = 0.79, p < 0.01 for GM-CSF and r = 0.87, p < 0.001 for IL-6). No inverse relationship between platelet-associated immunoglobulin G (PAIgG) and platelet count was observed (r = 0.39, p > 0.20). These findings suggest that the fluctuation of platelet count in this case may result from an aberration of the cytokine network regulating megakaryopoiesis and platelet formation.