Indirect study of thrombopoiesis (TPO, reticulated platelets, glycocalicin) in patients with hereditary macrothrombocytopenia

Chronic isolated hereditary macrothrombocytopenia (CHMT) is a congenital fo rm of macrothrombocytopenia that seems to be due to defective production se condary to a disturbance in megakaryocyte fragmentation. To better understa nd the pathogenesis of thrombopoiesis in this hereditary thrombocytopenic d isorder, we determined the percentage of reticulated platelets (RP), plasma glycocalicin (GC) and thrombopoietin (TPO) levels in 29 patients with CHMT , 23 patients with immune thrombocytopenic purpura (ITP), and 17 patients w ith thrombocytopenia secondary to decreased bone marrow megakaryocytes (hyp oplasia). The % RP was similar in CHMT (2.27 +/- 1.33) and hypoplasia (1.98 +/- 1.35) patients and markedly lower than that in ITP patients (8.80 +/- 7.97; p < 0.001), suggesting that the production of new platelets is reduce d in CHMT. Plasma GC was within the normal range (0.84 +/- 0.16 mu g/mL) bo th in patients with CHMT (0.63 +/- 0.20 mu g/mL) and ITP (0.82 +/- 0.90 mu g/mL), while it was significantly decreased in patients with hypoplasia (0. 16 +/- 0.04 mu g/mL; p < 0.001). When the GC value was normalized for plate let count, the GC index was normal in CHMT patients (2.05 +/- 1.1) and in p atients with hypoplasia (0.85 +/- 0.10) while it was significantly increase d in ITP patients (10.88 +/- 18.00; p < 0.001); thus, patients with CHMT se em to have a normal platelet turnover. TPO was significantly increased in C HMT (195 +/- 72 pg/ml) as compared with normal (80 +/- 53 pg/ml; p < 0.002) ; however, the mean level was not as high as in ITP patients (345 +/- 167 p g/mL; p < 0.001). This finding suggests that CHMT syndrome is not secondary to a defective production of TPO and that megakaryocyte mass is nearly nor mal.