Chapter 22 Extrinsic Defects Leading to Increased Erythrocyte Destruction - Nonimmune causes

what are non-immune extrinsic hemolytic anemias

disorders where RBCs are normal but outside conditions cause hemolysis (like physical or mechanical injury)

what is a microangiopathic hemolytic anemia

disorder where RBCs are damaged/fragmented intravascularly as cells pass through small blood vessels partially blocked by clots or damaged endothelium

what are some common morphologies found in peripheral smears of someone with microangiopathic hemolytic anemia

• schistocytes

• helmet cells

• microspherocytes

• polychromasia

• nRBCs

which of the following morphologies is NOT common in microangiopathic hemolytic anemias?

• target cells

• spherocytes

• schistocytes

• helmet cells

target cells

what is thrombotic thrombocytopenic purpura (TTP)

life-threatening disorder where platelets adhere to one another causing clots to form in the blood vessels

what causes thrombotic thrombocytopenic purpura (TTP)

a deficiency in ADAMTS13 protein (von Willebrand factor-cleaving protease)

what other clinical findings/symptoms can be associated with TTP

neurologic dysfunction, fever, and renal failure

what are some lab findings for TTP

severe thrombocytopenia and elevated LD

the best treatment for thrombotic thrombocytopenic purpura is

plasma exchange

what is Hemolytic Uremic Syndrome (HUS)

damage to blood vessel endothelial cells and RBCs from either Shigella or E. coli toxins OR unregulated activation of alternative complement pathway

what are the 2 types of HUS syndrome

• typical HUS - Shiga or E. coli O157:H7 toxin

• atypical HUS - unregulated activation of the alternative complement pathway

what other clinical findings/symptoms are associated with HUS

acute renal failure, abdominal pain, bloody diarrhea, fever, vomiting; typically affects children

what are some lab findings of HUS

• mild to moderate thrombocytopenia

• elevated serum creatinine

• proteinuria, hematuria

• hyaline, granular, and RBC casts

what is the best treatment for HUS

eculizumab (aHUS)

what is HELLP syndrome

a dangerous pregnancy complication closely associated with preeclampsia

• H = hemolysis

• EL = elevated liver enzymes

• LP = low platelet count

how is the severity of HELLP syndrome measured

serum LD & aspartate aminotransferase (AST)

what is the best treatment for HELLP syndrome

delivery of the fetus and placenta as soon as possible, along with supportive care to control electrolytes, fluid balance, HTN, and to prevent seizures

what is disseminated intravascular coagulation (DIC)

activation of coagulation cascade, causing clots throughout blood vessels

what are the clinical manifestations of disseminated intravascular coagulation (DIC)

organ damage - due to clots

bleeding - no more platelets or clotting factors = nothing clots → bleed out

what are disorders are associated with DIC

metastatic cancers, acute leukemias, infections, trauma, extensive burns, transfusion reaction, snake or spider venom

what test distinguishes DIC from HELLP syndrome

PT and PTT test

• DIC have prolonged PT and PTT

• HELLP have normal PT and PTT

what test distinguishes DIC from other microangiopathies

D-dimer test

what are some lab findings for DIC

• thrombocytopenia

• schistocytes

• PT and PTT prolonged

• fibrinogen decreased

• D-Dimer increased

this test is very useful for distinguishing DIC from other microangiopathic anemias

D-dimer

what is traumatic cardiac hemolytic anemia

hemolysis caused by prosthetic hearth valves

what are some lab findings in a patient with traumatic cardiac hemolytic anemia

• anemia

• schistocytes are very characteristic

• increased reticulocytes

• normal PLTs

• LD, indirect bilirubin, plasma Hgb are increased

• serum haptoglobin is decreased

• chronic forms can have hemosiderinuria and decreased serum ferritin

what RBC morphology is TYPICALLY found on the peripheral smear of a patient with traumatic cardiac hemolytic anemia

schistocytes

what is exercise-induced hemoglobinuria

hemolysis caused by excessive exercise in long-distance endurance events (running, cycling, swimming, etc.)

what are some typical lab findings in exercise-induced hemoglobinuria?

• anemia not usually caused unless hemoglobinuria is severe or recurrent

• decrease serum haptoglobin

• elevated free plasma hemoglobin

• hemoglobinuria after exercise

• slightly increased MCV and reticulocyte count

what are 4 mechanisms in a Plasmodium falciparum infection that can cause anemia

1. direct lysis of infected RBCs during reproduction of schizonts (parasite)

2. immune destruction of infected and noninfected RBCs in the spleen

3. inhibition of erythropoiesis and ineffective erythropoiesis

4. destruction of non-infected RBCs

most severe cases of malaria are due to …?

Plasmodium falciparumwhat

what other Plasmodium species cause severe disease

P. vivax and P. knowlesi

why does P. falciparum infection result in the most serious hemolysis of the various forms of malaria

all RBCs can be invaded

what causes baseiosis

infection with Babesia parasite from tick bite

what causes Clostridal sepsis

infection with Clostridium perfringens that can trigger DIC and renal failure

what is the morphology in peripheral smears of Clostridal sepsis

RBCs become spherical and toxic changes to neutrophils (blue-green crystals of death)

what causes Bartonellosis

infection by Bartonella bacilliformis bacteria from female sandfly endemic to Peru, Ecuador, and Colombia

• also known as “Carrion disease”

what do Heinz bodies indicate

hemolysis caused by drugs or chemicals

what type of hemolysis shows Heinz bodies and bite cells

hemolysis caused by venom

what type of hemolysis has schistocytes, speherocytes, and micospherocytes

extensive burns

Heinz bodies/bite cells may be present in blood films from patients with hemolytic anemia caused by

poisonous venom

Renal failure is a prominent feature of:

• hemolytic uremic syndrome

• thrombotic thrombocytopenia purpura

• Plasmodium malariae infection

• march hemoglobinuria

hemolytic uremic syndrome (HUS)

Which one of the following is a feature found in all microangiopathic hemolytic anemias?

• Pancytopenia

• Thrombocytosis

• Intravascular RBC fragmentation

• Prolonged PT and PTT

intravascular RBC fragmentation

Which of the following tests yields results that are abnormal in DIC but are usually within the reference interval or just slightly abnormal in TTP and HUS?

• Indirect serum bilirubin and serum haptoglobin

• Prothrombin time and partial thromboplastin time

• Lactate dehydrogenase and aspartate aminotransferase

• Serum creatinine and serum total protein

prothrombin time and partial thromboplastin time (PT and PTT)

What RBC morphology is characteristically found within the first 24 hours following extensive burn injury?

Schistocytes and microspherocytes