Agnogenic Myeloid Metaplasia (AMM)

AGNOGENIC MYELOID METAPLASIA (AMM)

Agnogenic myeloid metaplasia (AMM), also known as myelofi-brosis, is a chronic myeloproliferative disorder that arises from neoplastic transformation of an early hematopoietic stem cell. The disease is characterized by marrow fibrosis or scarring, spleno-megaly, extramedullary hematopoiesis (typically spleen, liver, or both), leukocytosis and thrombocytosis, and anemia. Some pa-tients have suppressed WBC and platelet counts as well as anemia (pancytopenia). Patients with AMM have increased angiogenesis (formation of new blood vessels) within the marrow. Early forms of blood cells (including nucleated RBCs and megakaryocyte frag-ments) are frequently found in the circulation. AMM is a disease of the elderly, with a median age at diagnosis of 60 to 65 years. Survival time varies from as little as 1 year to more than 30 years; the average is 4 to 5 years (Anderson, Hamblin, & Traynor, 1999). Heart failure, complications of marrow failure, and trans-formation to AML are the common causes of death.

Medical Management

Medical management is directed toward palliation, reducing symptoms related to cytopenias, splenomegaly, and hypermeta-bolic state. Although one third of anemic patients respond to the combination of an androgen plus a corticosteroid, the primary treatment remains RBC transfusion. Because of the prolonged re-quirement for RBC transfusion, iron overload is a common prob-lem. Iron chelation therapy should be initiated for those individuals in whom survival is expected to exceed a few years (Anderson Ham-blin, Traynor, 1999). Hydroxyurea is often used to control high WBC and platelet counts and to reduce the size of the spleen. Splenic irradiation or splenectomy may also be used to control the massive splenomegaly that can develop. However, both modalities render the patient at significant risk for development of infection. BMT may be a useful treatment modality in younger, otherwise healthy individuals.

Nursing Management

The extent of splenomegaly can be profound in patients with AMM, with enlargement of the spleen that extends to the pelvic rim. This condition is extremely uncomfortable to the patient and can severely limit nutritional intake. Analgesics are often ineffec-tive. Methods to reduce the spleen’s size are usually more effective in controlling pain. Splenomegaly, coupled with a hypermetabolic state, results in weight loss (often severe) and muscle wasting. Pa-tients benefit from very small, frequent meals of foods that are high in calories and protein. Weakness, fatigue, and altered body image are other significant problems. Energy conservation methods and active listening are important nursing interventions. Patients need to be educated about signs and symptoms of infection as well as ap-propriate interventions when an infection is suspected.