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Definition

Aplastic anemia is a disorder of hematopoiesis characterized by pancytopenia and a marked reduction or depletion of erythroid, granulocytic, and megakaryocytic cells in bone marrow.

In aplastic anemia, hematopoietic stem cells are unable to proliferate, differentiate, or give rise to mature blood cells and their precursors.

Etiology

1. Idiopatic : 50-65% cases.

2. Acquired :

· Drugs : antimetabolites, antimitotic agents, chloramphenicol, phenylbutazone, sulfonamides.

· Radiation

· Chemicals : benzene, solvents, insecticides.

· Viruses: non-A, non-B, non-C hepatitis, Epstein-Barr virus.

· Paroxysmal nocturnal hemoglobinuria.

· Miscellaneous: pregnancy, connective tissue disorders.

3. Hereditary :

· Fanconi anemia.

· Dyskeratosis congenital.

· Schwachman syndrome.

Clinical Manifestations

The most common initial symptoms of aplastic anemia are caused by anemia and thrombocytopenia:

· Progressive weakness

· Fatigue, headaches

· Dyspnea on exertion

· Petechia

· Ecchymoses

· Epistaxis

· Metrorrhagia

· Gum bleeding.

If the anemia is severe, the patient may be tachy-cardic and have cardiac murmurs associated with high-flow states. Hepatosplenomegaly and lymphadenopathy are notably absent.

Diagnostic Evaluation

The diagnosis of aplastic anemia should be considered if a pancytopenic patient :

· normochromic, normoc

ytic (or slightly macrocytic), and aregenerative anemia.

· Thrombocytopenia with normal-sized platelets.

· Neutropenia and no ab

normal cells in the leukocyte differential.

The absolute reticulocyte count is low because the anemia is secondary to reduced or absent red cell production.

Confirmation of the diagnosis requires morphologic and cytogenetic evaluation of the bone marrow (numerous spicules with empty fatty spaces and a few hematopoietic cells).

Differential Diagnosis

· hypocellular myelodysplastic syndrome.

· Hypocellular acute leukemia.

· Hairy cell leukemia.

Treatment

· Immunosuppressive Therapy

The treatment of choice for aplastic patients who lack a histocompatible sibling or are older than 40 years is ATG (40 mg/kg/day for 4 days) alone or in combination with cyclosporine (10 mg/kg/day divided into two doses, with dose adjustments as needed to maintain levels of 200 to 400 μg/mL for 3 to 6 months and then tapered over a period of 3 months).

· Allogeneic Hematopoietic Stem Cell Transplantation

The curative treatment for anemia aplastic is hematopoietic stem cell transplantation from an HLA-compatible sibling.

· Supportive Therapy

Red cell and platelet transfusions.

Prognosis

· The pancytopenia of aplastic anemia is progressive and life-threatening.

· The prognosis at diagnosis is closely correlated with the severity of neutropenia.

· The risk for infection (mainly bacterial and fungal) and associated mortality is high in patients with very severe aplastic anemia.