Background and purpose: Depending on the severity of the illness, thrombocytosis is found in about 60% to 70% of patients with Henoch-Schönlein purpura (HSP). Whether thrombocytosis is the result of an inflammatory reaction mediated by thrombopoietin (TPO) or other inflammatory cytokines such as interleukin (IL)-6 remains unknown.
Methods: Thirty two patients who met the diagnostic criteria for HSP were included. They were divided into two groups - HSP patients with thrombocytosis (n = 14) and those without thrombocytosis (n = 18) with a platelet count of 400,000/microL. Eight normal healthy controls were also included. TPO and IL-6 serum levels during the acute phase were measured by enzyme-linked immunosorbent assay.
Results: Patients with platelet counts greater than 400,000/microL in the acute stage had significantly lower TPO levels than patients with platelet counts lower than 400,000/microL (310 +/- 65.6 pg/mL vs 608 +/- 97.8 pg/mL, p=0.013). However, HSP patients with or without thrombocytosis had similar TPO levels as the healthy controls (441 +/- 176 pg/mL, p=0.89 and 0.29, respectively). IL-6 serum levels were significantly elevated in HSP patients during the acute stage of HSP (28.6 +/- 61.7 pg/mL vs 3.16 +/- 1.35 pg/mL, p=0.049). In patients with complications of glomerulonephritis or gastrointestinal hemorrhage (n = 12), IL-6 levels were significantly lower than in those without such complications (8.07 +/- 3.79 pg/mL vs 40.9 +/- 16.9 pg/mL, p=0.007).
Conclusions: This study showed that thrombocytosis in HSP patients is a type of inflammatory reactive thrombocytosis, and that IL-6 may also play a role in the pathogenesis of HSP.