0071643192.pdf

HEMATOLOGY, ONCOLOGY, ALLERGY,

AND IMMUNOLOGY

BETATHALASSEMIA

Occurs when one or both beta globin chain genes fails to function normally

■ Thalassemia minor

■ Asymptomatic

■ Hypochromic, microcytic anemia (Hb >10 g/dL)

■ Thalassemia intermedia

■ Symptoms of anemia

■ Hypochromic, microcytic anemia (Hb 7–10 g/dL)

■ May require transfusions

■ Thalassemia major(Cooley anemia)

■ Severe anemia, splenomegaly, frontal bossing

■ Requires transfusions to sustain life

■ Iron chelation therapy is required to prevent complications from chronic

transfusions.

■ Splenectomy may reduce transfusion requirements.

G6PD Deficiency

This X-linked recessive disorder results in RBCs that are more susceptible to

oxidant stress. Level of G6PD deficiency ranges from mild to severe. The dis-

ease is common in people of African, Asian, and Mediterranean descent.

PATHOPHYSIOLOGY

■ Oxidant stress (see Table 9.4) →hemoglobin precipitation within the

RBC→removal of cell from circulation via spleen.

SYMPTOMS/EXAM

■ Asymptomatic unless exposed to precipitant

■ Exposure results in hemolysis.

■ Hemolytic crisis = severe hemolysis with hemoglobinuria, jaundice, splenome-

galy, and possible vascular collapse.

■ Symptoms/findings consistent with cholelithiasis are common.

DIAGNOSIS

■ Peripheral smear showing Heinz bodies(RBCs with precipitated hemoglobin)

■ Measurement of enzyme levels

TABLE 9.4. Common Precipitants of Hemolysis in G6PD Deficiency

Drugs (oxidizing agents)

Dapsone, methylene blue, nitrofurantoin,phenazopyridine (pyridium), primaquine

sulfonamides, antimalarials

Infection

Fava beans