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Medical Significance of the Clinical manifestations Of Myeloproliferative Disorders: Myelofibrosis

Updated on February 3, 2014

Detecting Splenomegaly

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A General Overview

The disorders polycythemia vera (PV), chronic myeloid leukemia (CML), essential thrombocythemia and idiopathic myelofibrosis (IMF) are included under this broad group.

These disorders are grouped together since they arise from a common precursor stem cell which can proliferate and differentiate into one or other types. These disorders may show transformation into one or other types when followed up. Around 30% of cases of polycythemia vera develop chronic myelofibrosis, so also 70% of chronic myeloid leukemia, 10% of polycythemia vera may develop acute myeloid leukemia on follow up:

Primary Myelofibrosis

Also known as Agnogenic Myeloid Metaplasia, Myelosclerosis, Idiopathic myelofibrosis; it refers to the condition where there is diffused fibrosis of bone marrow, sometimes accompanied by osteosclerosis occurring as a primary abnormality. Compensatory hematopoiesis occurs in the spleen, bone marrow, lymph nodes and other organs. As the condition is fully established, reactive fibrosis occurs which replaces the hemopoietic tissues. Ossification may occur in these areas later.

Though, the disease is more common in adults past middle age, any age may be affected. Both sexes are equally affected, and rarely the disease may run in families. There is a higher incidence of myelofibrosis in children with Down’s syndrome.

Clinical features: The onset is insidious with vague ill health and development of abdominal mass. A majority of cases are mildly anemic with Hb 5-9 g/dl. The prominent feature is below the costal margin. Liver may be moderately enlarged up to 6-10 cm. Lymph node enlargement, mild jaundice and bleeding manifestations may be rarely present.

The classical blood picture is leukoerythroblastic anemia. Both immature erythroid and myeloid precursors are present in peripheral blood. The erythrocytes show marked aniso and poikilocytosis, polychromasia and “teardrop” appearance. There is moderate leucocytosis. Total leucocyte count may reach 20- 30,000/cmm. Platelet count is usually normal or increased and the morphology may be abnormal with many giant platelets. Megakaryocytic fragments may be seen in peripheral blood. In the late stages thrombocytopenia may occur. Platelet function may be defective.

Bone marrow aspiration usually gives a dry tap. Foci of extramedullary hematopoiesis can be demonstrated in the spleen, liver and rarely lymph nodes. Radiographs of bones show osteosclerosis with obliteration of marrow cavity. Changes are most markedly seen in the vertebrae, shafts of long bones of the extremities, ribs, clavicles and pelvis. Serum uric acid is increased. Leucocyte alkaline phosphatase is high.

Myelofibrosis Blood Film

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Gross Splenomegaly

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Diagnosis And Treatment

Diagnosis: Myelosclerosis should be suspected in any patient presenting with mild to moderate anemia, gross splenomegaly, leukoerythroblastic blood picture, and repeated dry taps of the bone marrow.

The condition has to be differentiated from chronic myeloid leukemia (CML). In CML, splenomegaly is directly proportional to the leukocyte count, leukocyte alkaline phosphatase activity is low. Philadelphia chromosome may be demonstrated.

Leucoerythroblastic blood picture may be encountered in acute hemolytic crisis, sudden hemorrhage, secondaries in the bone marrow and secondary myelofibrosis.

Course and prognosis: The disease follows a protracted course with the median survival period of 3-4 years. With judicious management, many cases live up to 10 years or more. When the spleen assumes a large size, hyper-splenism may develop.

Complications:These are hypersplenism, surgical complications of the spleen, development of acute myeloid leukemia, secondary gout and hemorrhages.

Treatment: There is no specific therapy, it is symptomatic. When there is evidence of hyperplasia of bone marrow and hypermetabolism, busulfan given in doses of 2-4 mg/day may be symptomatically beneficial. Splenectomy acts as a source of blood cells, but if hyper-splenism develops, splenectomy is indicated. Isotopic studies help in determining whether the spleen is more active in producing or destroying blood cells.

Secondary Myelofibrosis

This occurs as a terminal complication of polycythemia vera, chronic myeloid leukemia, disseminated tuberculosis involving the bone marrow, irradiation, toxicity to drugs like benzene and chloramphenicol, secondary carcinoma affecting the bone marrow, Paget’s disease of bone and Albers-Schonberg’s disease.

© 2014 Funom Theophilus Makama

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