Color Atlas of Hematology - Practical Microscopic and Clinical ...

168Erythrocyte and Thrombocyte AbnormalitiesThrombocytopenias Due to Reduced Cell ProductionIn this condition, blood contains few, usually small, pyknotic (“old”)thrombocytes. Only a very few megakaryocytes are found in the bonemarrow, and these have a normal appearance.CausesChronic alcoholism. There may be some overlap with increased turnoverand folic acid deficiency.Chemical and radiological noxae. Cytostatics naturally lead directly to adose-dependent reduction in megakaryocyte counts. A large therapeuticradiation burden in the area of blood-producing bone marrow has thesame result, which may persist for many months.Virus infections. Measles, mononucleosis (Epstein–Barr virus, cytomegalovirus),rubella, and influenza may (usually in children) trigger thrombocytopeniasof various types. In these cases, the virus affects the megakaryocytesdirectly. However, antibodies to thrombocytes may also arisein the course of these infections (p. 166), so that the pathomechanism ofthe parainfectious thrombocytopenias described by Werlhof in childrenmay lie in impaired production and/or increased degradation of thrombocytes.Neoplastic and aplastic bone marrow diseases. All neoplasms of the bonemarrow cell series (e.g., leukemia, lymphoma, and plasmacytoma), togetherwith their precursor forms (e.g., myelodysplasia), lead to progressivethrombocytopenia, as do panmyelophthisis and bone marrow infiltrationby metastases from solid tumors.Vitamin deficiency. Folic acid and vitamin B 12 deficiencies from variouscauses (p. 152) also affect the rapidly proliferating megakaryocytes. Inthese cases, thrombocytopenia is often present before anemia andleukocytopenia in circulating blood, while the bone marrow showscopious megakaryocytes that have been blocked from maturation.Constitutional diseases. An amegakaryocytic thrombocytopenia withoutany of the above causes is rare. It is seen in children with congenital radialaplasia; in adults it tends usually to be an early sign of leukemia,myelodysplastic syndrome, or aplastic anemia.Wiscott-Aldrich syndrome (thrombocytopenia, immune deficiency, andeczema) is an X-chromosomal recessive disease in boys and presents withthrombocytopenia with ineffective megakaryopoiesis.The May-Hegglin anomaly (dominant hereditary transmission) ischaracterized by thrombocytopenia with giant thrombocytes andgranulocyte inclusions, which resemble Döhle bodies (endoplasmatic reticulumaggregates).