RESUMEN
Acquired amegakaryocytic thrombocytopenia (AAT) is a rare hematological disorder causing severe thrombocytopenia and bleeding. Previous in vitro studies postulated both cell-mediated suppression of megakaryocytopoiesis in early megakaryocytic progenitor cells and humoral-mediated suppression by anti-thrombopoietin antibodies as possible etiologies of AAT. Patients with AAT usually present with severe bleeding and thrombocytopenia that is unresponsive to steroids and intravenous immunoglobulin (IVIG). Although standard guidelines have not been established for management of AAT, a few case reports have indicated a response to immunosuppressive treatment. The prompt recognition of this disease entity is essential in view of the substantial risk of morbidity and mortality from excessive bleeding. We report a case of AAT successfully treated with equine antithymocyte globulin (ATG) and cyclosporine (CSP).
RESUMEN
Developmental differences in megakaryocytes between neonates and adults have been described. However, the age at which megakaryocytes make a transition to an adult phenotype is unknown. Small megakaryocytes are often described as "dysplastic" in the pathology literature. Thus, recognizing the normal features of megakaryocytes at different ages has diagnostic implications. We identified 72 samples from 61 patients, aged 3 days to 80 years, who had negative staging based on bone marrow examination. Megakaryocyte diameters, as highlighted with anti-CD61, were measured. A scatter plot of megakaryocyte size by age revealed a normal distribution of sizes at the youngest ages, with a shift to multiple peaks starting at 24 months indicating that neonates have megakaryocytes of uniform sizes, which diverge into separate clusters of smaller and larger cells beginning at 2 years; this is followed by an overall shift toward larger megakaryocytes at age 4 years. These observations have direct implications for the evaluation of bone marrow megakaryocytes in young children.
