A patient presents with a platelet count of 700 x 109/L with abnormalitites in size, shape and granularity of platelets. WBC count of 12 x 109 L, hemoglobin of 11g/d1 and the absence of the Philadelphia chromosome. The most likely diagnosis would be-

Ans. is 'b' i.e., Essential thrombocythemiao Presence of increased thrombocytes and increased leukocytes in the absence of any other hematological abnormality suggests the diagnosis of essential thrombocythemia.o Essential thrombocytosis is a clonal disorder of unknown etilogy involving a multipotent hematopoietic progenitor cell and is manifested clinically by the overproduction of platelets without a definable cause.Essential thrombocythemia Clinical featuresClinically essential thrombocytosis is most often identified incidentally when a platelet count is obtained during the course of a routine evaluation.The platelet count is usually > 600 x 109/L in peripheral blood and an abnormal increase of megakaryocytes in bone marrow. o No symptoms or signs are specific for essential thrombocytosis but patients do have hemorrhagic and thrombotic tendencies.o Hemorrhagic manifestations of Essential thrombocytosis are : Excessive bleeding occurs spontaneously or following trauma. There is mucosal (gastrointestinal) or skin bleeding (bruising)o Thrombotic manifestaions of Essential thrombocytosis are : Deep vein thrombosis is seen in about a quaer of cases. Aerial thrombotic manifestaitons are more frequent. There may be coronary, cerebral or peripheral vessel involvement. Signs of ischemia of toes in the form of pain and change in colour is noted. Cerebrovascular occlusion results in headache, dizziness and focal seizures.Physical examination.o Physical examination is generally unremarkable except occasionally for mild splenomegaly (Massive splenomegaly is more characteristic of other myeloproliferative disorders.)Blood FindingsIncreased platelet count (criteria suggested is platelet count > 600 x 109/L).o Platelets are large and hypo granular along with normal sized plateleto TLC T (mild leucocytosis)o Hemoglobin normalo NAP score increasedBone marrowo Hypercellular marrowo Megakaryocytic hyperplasiao There are clusters of megakaryocytes which are normal in size along with giant megakaryocytes and Megakaryocytes with features of dysmegakaryopoiesis.