MYELOPROLIFERATIVE DISORDERS

Myeloproliferative disorders are abnormal proliferation of one or more bone marrow cell lines. Four types are recognized. Polycythemia vera is mostly a disease of increased red blood cells. Chronic myelogenous leukemia (CML) is a disease of the white blood cell series. Essential thrombocytosis presents itself with an abnormally elevated platelet count. Myelofibrosis frequently manifests itself with low blood cell counts secondary to bone marrow fibrosis from overgrowth of blood cell precursors. All these conditions originate from an abnormality in the early blood cell progenitors and may evolve into acute leukemia.

The cause of myeloproliferative disorders is unknown. Survivors of atomic bomb explosions and patients treated with radiation for some types of cancer have an increased incidence of CML.

Myeloproliferative disorders are uncommon. Polycythemia vera occurs among 5 per 1 million persons per year; the other subtypes are less frequent. The mean age of patients is 60 years. Myeloproliferative disorders occur sporadically. They are not contagious.

Patients with elevated blood cell counts should undergo examination of a blood smear and bone marrow, which help establish the diagnosis. Additional tests, such as red blood cell counts and measurement of plasma volumes for polycythemia vera and platelet function for essential thrombosis may be necessary. It is important to rule out elevation of blood cell counts due to other conditions, such as lung disease, smoking, congenital heart anomalies, infections, tumors, and iron deficiency. Analysis of the genetic material (chromosomes) is essential to detect Philadelphia chromosome, which is diagnostic of CML.

Patients with polycythemia vera, essential thrombosis, or myelofibrosis can be treated effectively with specific medications. However, these disorders cannot be eradicated. Patients with CML can undergo curative bone marrow transplantation.

An increase in red blood cells causes an increase in blood viscosity and clotting. Elevation of the platelet count in essential thrombosis can predispose a person to both thrombosis and bleeding. Myelofibrosis can first present itself with elevated blood cell counts but uniformly leads to lowering of these counts. Anemia and low white blood cell and platelet counts follow. Breakdown of the increased number of blood cells leads to an increase in uric acid. Most patients have an enlarged spleen, and many have an enlarged liver.

Increased viscosity can manifest itself as ruddy complexion, headaches, visual disturbances, lightheadedness, and shortness of breath. Patients with myeloproliferative disorders are at risk for strokes, heart attacks, and impaired circulation in the legs. Pain and whitening in the fingers and toes can occur. Bleeding from the mouth or gastrointestinal tract and easy bruising may be noticed. Itching, especially after a hot bath, is characteristic of polycythemia vera. An enlarged spleen can cause pain, heaviness in the left side of the abdomen, and a feeling of early satiety. An increased uric acid level can cause kidney stones and swelling of the joints (gout). Low blood cell counts show as anemia, fatigue, and pallor. A low white blood cell count predisposes to infections and a low platelet count to bleeding.

Hydroxyurea is administered as a pill daily, depending on your blood cell counts. Your physician monitors the blood counts and adjusts the dose.

The chemotherapeutic drug hydroxyurea controls elevated blood cell counts for most patients. Anagrelide is indicated for elevated platelet counts in essential thrombosis and other conditions. Patients with polycythemia vera need treatment with regular phlebotomies (blood letting). Radioactive phosphorus is rarely used, mostly for elderly patients with polycythemia vera and essential thrombosis. Patients with anemia of myelofibrosis can benefit from use of androgen hormones and may need transfusions. Splenectomy or radiation to the spleen may offer relief to patients with painfully enlarged spleens.

Patients with CML receive specific treatment with interferon-alfa and chemotherapeutic agents. Young patients may undergo bone marrow transplantation.

Hydroxyurea can lower the white blood cell count and cause a rash and abdominal discomfort. Androgenic hormones can cause abnormal liver function and hair growth in a male pattern. Interferon-alfa can cause fever, fatigue, and flu-like symptoms.

Use of radioactive phosphorus is associated with increased risk for leukemia. For this reason it is reserved for elderly patients who are intolerant of other therapies. Anagrelide can worsen symptoms among patients with congestive heart failure. Interferon-alfa can cause abnormal liver and kidney function.

The complications of bone marrow transplantation are infection, toxic effects on the internal organs, and graft-versus-host disease, in which donor cells attack the recipient.

Phlebotomies are the treatment of choice among younger patients with polycythemia vera. The procedures are performed every other day initially (more cautiously for patient with heart disease or who have had a stroke). When the red blood cell count stabilizes, phlebotomy can be performed monthly. Patients who undergo any surgical procedure may need additional phlebotomies before the operation.

Anagrelide is a pill taken daily. Platelet counts should be regularly checked. Interferon is given as an injection under the skin, every day or every other day. Dose adjustments are necessary, depending on the tolerance of the drug. Allopurinol lowers uric acid level and prevents kidney stones and gout. Antihistamines improve itching for patients with polycythemia vera. Aspirin improves tenderness of the toes and fingers.

• Take your medications as prescribed.
• Keep appointments with your physician for blood counts and dosage adjustments.
• Keep your phlebotomy appointments.
• Have your platelet counts checked regularly if you are taking anagrelide.
• Discuss your other medications with a medical professional; the drugs may interfere with your treatment.

• Do not take aspirin without consulting your physician.
• Abstain from fresh leafy vegetables and fruit, cheeses and yogurt if you have a low white blood cell count.
• Avoid interactive, potentially traumatic sports, because of bleeding risk.

• If you have fatigue, chest pain, or shortness of breath that does not resolve with rest.
• If you have severe headaches, sudden weakness in one arm or leg, difficulty speaking, fever, or bleeding.

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