12) Hemolytic anemia—nonimmune defects Flashcards
2 types of extrinsic factors that can cause hemolytic anemia
- immune
- nonimmune
general categories of nonimmune causes of hemolysis
- physical trauma to RBC (MAHA, malignant HTN, exercise, heat, heart valve)
- antagonists (toxins, infectious agents)
general antagonist behind the hemolysis in HUS, TTP and DIC
thrombi in microcirculation
snake bites often cause mechanical damage to RBCs via…
DIC
general signs of traumatic injury to RBCs on PB and in chemistry
- schistocytes/helmet cells
- ↑ retics/polychromasia
- striking poik
- signs of IV hemolysis (hemoglobinuria, ↓ hapto, ↑ LD, ↑ unconjugated bilirubin)
general term indicating RBCs are lysed or damaged by microcirculatory lesions or shear forces in circulation
microangiopathic hemolytic anemia (MAHA)
explain the process of MAHA
- endothelial lining of small vessels damaged
- platelets & fibrin deposits form
- thrombus formation in vessels
- RBCs forced through fibrin strands in thrombus, causing fragmentation
MAHA hemolysis is (intravascular/extravascular)
depends on severity
less damage —EV
more damage —IV
examples of MAHA disorders
- HUS
- TTP
- DIC
- malignant HTN
- disseminated cancer
- preeclampsia/eclampsia
- HELLP syndrome
triad of HUS s/s
- hemolytic anemia with schistocytes
- thrombocytopenia
- acute nephropathy/renal failure
2 groups of HUS
- D+HUS—diarrhea —90% cases, mostly children <5 —caused by shiga toxin
- D=HUS —no diarrhea —atypical HUS
causes of D+HUS
- E. coli O157:H7
- Shigella dysenteriae serotype I
causes of D=HUS
- postinfection (Spne, viruses)
- immunosuppression (chemo)
- renal/BM transplantation
- pregnancy
- OC
- toxins
how does shiga toxin cause HUS?
- enters circulation through tears in colon mucosa
- damages endothelial cells in glomeruli
- platelet activation & fibrin microthrombi form
- erythrocytes are damaged & kidney loses function
acute onset
bloody hematuria
sudden pallor
abd pain
vomiting
bloody diarrhea
HUS
(TTP/HUS) has less severe CNS sx if present.
HUS
Hgb in HUS
7-9 g/dL, some requiring transfusion
HUS on PB
- normo/normo
- schistocytes, helmet cells
- spherocytes
- polychromasia
- occasional nRBCs
- left shift of leukocytosis
- platelet count low to markedly low
HUS chemistry findings
- signs of IV hemolysis
- ↑ BUN, creatinine
- hypokalemia, hyponatremia
- proteinuria, hematuria, pyuria
HUS coag tests
normal to slightly elevated
plasma exchange may be indicated in —- HUS
D=
new tx for HUS
monoclonal Ab against shiga toxin