MEDizzy - A 68-year-old man seeks evaluation for fatigue, weight loss,

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Combined hemotology IV

A 68-year-old man seeks evaluation for fatigue, weight loss, and early satiety that have been present for about 4 months. On physical examination, his spleen is noted to be markedly enlarged. It is firm to touch and crosses the midline. The lower edge of the spleen reaches to the pelvis. His hemoglobin is 11.1 g/dL, and hematocrit is 33.7%. The leukocyte count is 6200/µL, and platelet count is 220,000/µL. The white cell count differential is 75% PMNs, 8% myelocytes, 4% metamyelocytes, 8% lymphocytes, 3% monocytes, and 2% eosinophils. The peripheral blood smear shows teardrop cells, nucleated red blood cells, and immature granulocytes. Rheumatoid factor is positive. A bone marrow biopsy is attempted, but no cells are able to be aspirated. No evidence of leukemia or lymphoma is found. What is the most likely cause of the splenomegaly?

ExplanationChronic idiopathic myelofibrosis (IMF) is the least common myeloproliferative disorder and is considered a diagnosis of exclusion after other causes of myelofibrosis have been ruled out. The typical patient with IMF presents in the sixth decade, and the disorder is asymptomatic in many patients. Fevers, fatigue, night sweats, and weight loss may occur in IMF whereas these symptoms are rare in other myeloproliferative disorders. However, no signs or symptoms are specific for the diagnosis of IMF. Often marked splenomegaly is present and may extend across the midline and to the pelvic brim. A peripheral blood smear demonstrates the typical findings of myelofibrosis including teardrop-shaped red blood cells, nucleated red blood cells, myelocytes, and metamyelocytes that are indicative of extramedullary hematopoiesis. Anemia is usually mild, and platelet and leukocyte counts are often normal. Bone marrow aspirate is frequently unsuccessful because the extent of marrow fibrosis makes aspiration impossible. When a bone marrow biopsy is performed, it demonstrates hypercellular marrow with trilineage hyperplasia and increased number of megakaryocytes with large dysplastic nuclei. Interestingly, individuals with IMF often have associated autoantibodies, including rheumatoid factor, antinuclear antibodies, or a positive Coomb’s tests. To diagnose someone as having IMF, it must be shown that they do not have another myeloproliferative disorder or hematologic malignancy that is the cause of myelofibrosis. The most common disorders that present in a similar fashion to IMF are polycythemia vera and chronic myelogenous leukemia. Other nonmalignant disorders that can cause myelofibrosis include HIV infection, hyperparathyroidism, renal osteodystrophy, systemic lupus erythematosus, tuberculosis, and marrow replacement in other cancers such as prostate or breast cancer. In the patient described here, there is no other identifiable cause of myelofibrosis; thus chronic idiopathic myelofibrosis can be diagnosed.