Myelofibrosis and acute megakaryoblastic leukemia in a child: topographic relationship between fibroblasts and megakaryocytes with an alpha-granule defect.
In a child with acute megakaryoblastic leukemia--severe thrombocytopenia and myelofibrosis, EM studies on bone marrow showed a strict topographic relationship between the presence of clusters of abnormal megakaryocytes and the increased number of fibroblasts and extracellular fibers. Megakaryocytes and platelets lacked alpha-granules while the plasma thromboglobulin level was three times the normal level. This suggested that the alpha-granular proteins were synthesized but not retained in alpha-granules. If this occurs, the increased marrow levels of platelet-derived growth factor and factor 4 would favor the proliferation of fibroblasts and the synthesis of collagen, and thereby promote myelofibrosis. After therapy-induced remission, the number of marrow megakaryocytes decreased, the alpha-granules were normally produced, the plasma beta-thromboglobulin level was normal and the myelofibrosis disappeared. These observations suggest that during acute megakaryoblastic leukemia, an acquired gray-platelet syndrome occurs and that the local excretion of alpha-granule proteins triggers the myelofibrosis.
D001792:Blood Platelets / Q000648:ultrastructure; D001853:Bone Marrow / Q000473:pathology / Q000648:ultrastructure; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008533:Megakaryocytes / Q000648:ultrastructure*; D008854:Microscopy, Electron; D055728:Primary Myelofibrosis / Q000097:blood / Q000150:complications* / Q000473:pathology; D013920:Thrombocythemia, Essential / Q000097:blood / Q000150:complications* / Q000473:pathology; D001620:beta-Thromboglobulin / Q000097:blood
D001620:beta-Thromboglobulin