0071643192.pdf

HEMATOLOGY, ONCOLOGY, ALLERGY,

AND IMMUNOLOGY

Microangiopathic Hemolytic Anemia

Mechanical disruption of RBCs in circulation, resulting in fragmentation
hemolysis

CAUSES

■ Disseminated intravascular coagulation (DIC)
■ Thrombotic thrombocytopenic purpura (TTP)
■ Hemolytic uremic syndrome (HUS)
■ Artificial heart valve
■ Pregnancy
■ Malignant HTN
■ Malignancies

THROMBOTICTHROMBOCYTOPENICPURPURA

■ Pregnancy, HIV, cancer, and noncancer immunosuppressive medications
(eg, cyclosporine) are associated with TPP.
■ Patients often present with fever and vague symptoms. Low platelets on
CBC usually prompts consideration of the diagnosis.
■ The classic pentad (fever, anemia, thrombocytopenia, renal failure, and
neurology problems) is rarely seen on presentation.
■ Neurologic symptoms may include AMS, seizures, and focal neurologic
deficits.
■ The cornerstone of treatment for TTP is plasma exchange transfusion.
Other treatments to be considered include:
■ Plasma transfusion (if exchange not available)
■ High-dose steroids (unclear benefit)
■ Splenectomy (if unresponsive to plasma exchange)
■ Aspirin (controversial)
■ Platelet transfusion is associated with rapid deteriorationand should not
be given to patients with TTP.

HEMOLYTICUREMICSYNDROME

■ HUS is typically preceded by infectious diarrhea(90%) caused by entero-
hemorrhagicE. coli, particularly E. coli0157:H7, shigella, or salmonella
containing the Shiga toxin. It may be preceded by URI (10%).
■ Identified exposures to E. coli0157:H7 include unwashed lettuce, poorly
cooked hamburger, unpasteurized dairy products, and petting cows.
■ Antimotility drugs and antibiotics may increase the risk of HUS.
■ HUS is more common in children than adults.
■ Patients typically present with diarrhea. The diarrhea may be grossly
bloody. Petechiae and purpura are also common.
■ Most patients will recover with only supportive therapy. Severe cases of HUS
are treated with plasma exchange. Antibiotics are generally discouraged
and may increase the likelihood of HUS and increase toxin production.

POLYCYTHEMIA

Polycythemia is characterized by an increase in RBC count, hemoglobin
(men>17 g/dL, women 15 g/dL), and blood volume. Primarypolycythemia is
called polycythemia vera and is regarded as a hematologic malignancy. Sec-
ondarycauses include conditions that increase EPO levels such as lung dis-
ease, heart disease, high altitude, EPO secreting tumors.

Symptoms of TTP—

FAT RN

Fever

Anemia

Thrombocytopenia

Renal Failure

Neurologic problems

E. coli0157:H7 is found in the

GI tract of healthy cows.

HUS: Microangiopathic

hemolytic anemia with renal

failure usually precipitated by

infectious bloody diarrhea

HSP: Vasculitis with

abdominal pain, palpable

purpura, and hematuria

usually precipitated by a URI;

bloody diarrhea may occur as

a result