APLASTIC AND HYPOPLASTIC ANEMIASWhat happens when the bone marrow shuts down?

APLASTIC ANEMIA Aplastic anemia is a severe, life

threatening syndrome in which production of erythrocytes, WBCs, and platlets has failed.

Aplastic anemia may occur in all age groups and both genders.

The disease is characterized by peripheral pancytopenia and accompanied by a hypocellular bone marrow.

HYPOCELLULAR BONE MARROW IN APLASTIC ANEMIA

APLASTIC ANEMIA Pathophysiology:

The primary defect is a reduction in or depletion of hematopoietic precursor stem cells with decreased production of all cell lines. This is what leads to the peripheral pancytopenia. This may be due to quantitative or qualitative

damage to the pluripotential stem cell. In rare instances it is the result of abnormal

hormonal stimulation of stem cell proliferation or the result of a defective bone marrow

microenvironment or from cellular or humoral immunosuppression

of hematopoiesis.

Pathophysiology of aplastic anemia

APLASTIC ANEMIA

APLASTIC ANEMIAInfections – viral and bacterial infections

such as infectious mononucleosis, infectious hepatitis, cytomegalovirus infections, and miliary tuberculosis occasionally lead to aplastic anemia

Pregnancy (rare)Paroxysmal nocturnal hemoglobinuria – this

is a stem cell disease in which the membranes of RBCs, WBCs and platlets have an abnormality making them susceptible to complement mediated lysis.

Other diseases – preleukemia and carcinoma

PNH

APLASTIC ANEMIA

APLASTIC ANEMIA Lab findings

Severe pancytopenia with relative lymphocytosis (lymphocytes live a long time)

Normochromic, normocytic RBCs (may be slightly macrocytic)

Mild to moderate anisocytosis and poikilocytosisDecreased reticulocyte countHypocellular bone marrow with > 70% yellow

marrow Treatment – in untreated cases the prognosis is poor

Remove causative agent, if knownMultiple transfusionsBone marrow transplant

RELATED DISORDERS Disorders in which there is peripheral

pancytopenia, but the bone marrow is normocellular, hypercellular, or infiltrated with abnormal cellular elements Myelopthesic anemia – replacement of bone

marrow by fibrotic, granulomatous, or neoplastic cells

RELATED DISORDERS Myelodysplastic syndromes – are primary,

neoplastic stem cell disorders that tend to terminate in acute leukemia. The bone marrow is usually normocellular, or

hypercellular with evidence of qualitative abnormalities in one or more cell lines resulting in ineffective erythropoiesis and/or granulopoiesis and/or megakaryopoiesis.

The peripheral smear shows dysplastic (abnormality in development) cells including nucleated RBCs, oval macrocytes, pseudo-Pelger-Huet PMNs (hyposegmented neutrophils) with hyperchromatin clumping, hypogranulated neutrophils, and giant bizarre platlets.

Hypersplenism – why can this lead to pancytopenia?

PURE RED CELL APLASIA Pure red cell aplasia is characterized

by a selective decrease in erythroid precursor cells in the bone marrow. WBCs and platlets are unaffected.Acquired

Transitory with viral or bacterial infections Patients with hemolytic anemias may suddenly

halt erythropoiesis Patients with thymoma – T-cell mediated

responses against bone marrow erythroblasts or erythropoietin are sometimes produced.

PURE RED CELL APLASIA Congenital

Diamond-Blackfan syndrome – occurs in young children and is progressive. It is probably due to an intrinsic or regulatory defect in the committed erythroid stem cell.

OTHER HYPOPROLIFERATIVE ANEMIAS Renal disease – due to decreased

erythropoietin Endocrine deficiencies – may lead to

decreased erythropoietin production. For example: hypothyroidism leads to decreased

demand for oxygen from tissues; decreased androgens in males; decreased pituitary function