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A 44-year-old woman went to her physician as part of a physical examination for life insurance. Her medical history was unremarkable, but she did complain of loss of appetite with a full feeling in her upper abdomen. She appeared to be in good physical condition but her spleen was palpable. Her physician ordered a complete CBC. What condition could cause an enlarged spleen?

Answer

An enlarged spleen can occur primarily as a result of hemolysis and sequestered cells or as a result of extramedullary hematopoiesis. In this case, the CBC revealed a 50,000 white count and a differential that showed the entire family of white cells. An LAP was ordered, and it was negative. This patient was diagnosed with early-stage chronic myelocytic leukemia. She was in no acute distress, but she was cautioned that since her spleen was enlarged, her movements should be restricted so as not to cause a rupture.

Summary Points

• Chronic myeloproliferative disorders (CMPDs) are caused by abnormal stem cells that lead to unchecked autonomous proliferation of one or more cell lines.

• The most common CMPDs are chronic granulocytic leukemia, polycythemia vera (PV), myelofibrosis with myeloid metaplasia (MMM), and essential thrombocythemia (ET).

The bone marrow in CMPDs may show hyperplasia or elements of fibrosis.

Most of these disorders are seen in older adults and show a normochromic normocytic process.

Individuals with chronic myelogenous leukemia (CML) show an extremely high white count, moderate anemia, and the entire spectrum of white cells in the peripheral smear.

200 Part III • White Cell Disorders

• Ninety percent of CML individuals show the Philadelphia chromosome, which is a cytogenetic abnormality in which a small part of chromosome 9 is translocated to the broken arm of chromosome 22.

• A hybrid gene, BCR-ABL, is also manifested with Philadelphia chromosome, and this gene prevents natural cell death or apoptosis.

• In the accelerated phase of CML, a higher blast count may be present and eventually ends in blast crisis, all blasts in the bone marrow.

• PV is a clonal disorder of red cells in which the patient shows a pancytosis: high red count, high white count, and high platelet count.

• Patients with PV have symptoms related to hypervis-cosity, including hypertension and vascular abnormalities.

• The leukocyte alkaline phosphatase score is usually elevated in PV and low in CML.

• Patients with PV must be distinguished from those with secondary or relative erythrocytosis.

• The major causes of death in patients with PV are hemorrhage and thrombosis.

• MMM is characterized by marrow fibrosis, extramedullar hematopoiesis, and the leukoery-throblastic blood smear.

• In patients with MMM, the accelerating fibrosis may contribute to leukopenia and thrombocy-topenia.

• In 50% of patients with MMM, bone marrow aspirates are impossible because of increased fibrosis: the dry tap.

• MMM has the worst prognosis of all of the myelo-proliferative disorders.

• ET is a clonal proliferation of megakaryocytes in the bone marrow.

• The peripheral count of patients with ET is extremely elevated, sometimes up to 1 million.

• The increased platelet count in ET can cause hemor-rhagic and thrombotic episodes, including gastrointestinal bleeding, epistaxis, and transient ischemic attacks.

• Diagnosis for ET involves ruling out any other causes for reactive thrombocytosis other than the clonal proliferation of megakaryocytes.

A 45-year-old male police officer sustained a fall from his motorcycle while driving at low speed while on patrol. He started to experience light-headedness, headache, and left upper quadrant abdominal pain. He was brought to a local hospital emergency department. On the basis of a physical examination, he was scheduled for surgery for a ruptured spleen. A STAT CBC was performed prior to surgery, with the following results:

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