12-1: 1/4 - Hemolytic Anemias

Anemia in which RBCs have shortened lifespan (under 120 days)

RBC enters spleen
Hgb broken down into Porphyrins
Releases CO, Fe, Unconjugated Bilirubin (aka Indirect bilirubin)

Liver conjugates bilirubin
Goes to gut--->Urobilogen-->stool, urine

Mostly pathologic

Red cell membrane liberates Hgb into blood stream

Haptoglobin binds free Hgb; complex goes to liver and is handled just like in spleen (to uribilin); but haptoglobin is easily saturated

Free Hgb (remaining) will go to kidney:
Excreted in urine as hemoglobinuria or hemosiderinuria

-Reticulocytosis
-Inc'd LDH (RBCs are rich in LDH)
-Inc'd indirect (unconj'd) bilirubin
-Inc'd urinary urobilinogen

-Absent haptoglobin
-Positive serum free Hgb
-Positive urinary hemosiderin or hemoglobinuria

SA:Vol ratio--biconcave disc exhibits excess membrane. allows cell to change shape without breaking.

Internal viscosity

Material properties allows RBCs to slide past one another

Consequence of deficiency of proteins coupling cytoskeleton to lipid bilayer of RBC membrane

Correlates with sprectin levels
Dec'd spectrin-->dec'd mechanical stability of RBC; progressive loss of elements of lipid bilayer-->lose SA without loss of volume-->spherocytes

Repeated RBC passes through spleen promotes membrane loss (gets stuck on way through spleen) and ultimately becomes spherical.

Spherocytes trapped in hostile splenic environment and die prematurely

Anemia
Jaundice (more bilirubin)
Splenomegaly
Gallstones (50% of patients with HS)
Crises

Aplastic: transient BM suppression by virus (Parvo B19)--BM turning over more rapidly, thus, more susceptible to infection

Inc'd baseline hemolytic rate: usually secondary to infection

Megaloblastic crisis: associated with folate depletion

If put RBCs in normal saline-->no hemolysis
In progressively more dilute NaCl-->inc'd hemolysis

Patients with HS will hemolyze earlier (with less dilute solution).

-Folate, RBC transfusion during crises
-Splenectomy (small risk of sepsis)--not req'd, but definitive tx

Fe2+

Hexomonophosphate shunt, which produces NADPH and pentoses. Requires G6PD!

B- normal
A+: African normal
A-: Common clin sig variant (G6PD deficiency)
G-6PD Med: common caucasian variant

Hemolysis with G6PD deficiency only seen in times of oxidative stress; infection, drugs

Pac man cell!

Need a Heinz body prep, can't be seen on regular smear.

Sign of G6PD def.

GdA-:
Black populns
Moderate hemolysis
Old red cells aff'd
Hemolysis w/drugs: unusual
Hemolysis with infection: common
NO need for transfusions

GdMed:
Seen in Mediterranean pops
Severe hemolysis
Seen in ALL rbcs
Hemolysis w/drugs common
Hemolysis w/infection common
Sometimes need transfusion

Cold: auto-ab active at temps below 37º, almost always IgM

Warm: auto-ab active at body temp, almost always IgG

Primary: aka idiopathic; no underlying or associated disorder

Secondary: underlying or associated disorder present, ex:
lymphoproliferative disorders
rheumatic disorders, SLE
infections: mono, pneumonia
drugs (alpha-methyldopa)**

Idiopathic (53%)
Lymphoma (18%)

Diagnoses presence of warm auto-ab's on RBCs

Direct: are there auto-ab's on RBC membrane?

Indirect: are their ab's in plasma?

Indirect method:
Patient's plasma in vial
Add RBCs expressing known Ab's (forms Ab-Ag complexes with RBCs)

Add anti-human globulin
If RBCs bound with Ab (from plasma)-->agglutination (positive result)

Patient RBCs in test tube
Add Anti-IgG

If IgG Ab's or complement present on pt's RBCs, cells will agglutinate (positive result).
Diagnosis of warm auto-ab.

Prednisone--high initial response rate, but as taper steroids, 50% of pts relapse

Splenectomy

Idiopathic (51%)
Mycoplasma (31%)

Cold IgM:
Intra- and extravascular hemolysis (extra bc of C3B, intra bc terminal lytic sequence of complement activated)

Plasma Hgb: high

Urine hemosiderin: +

Haptoglobin: low low

Gamma Coombs': directed against IgG; negative

Non-gamma Coombs' is in regard to complement; positive

Acrocyanosis--pts with cold auto-ab's, blood reaching arterioles results in correlation-->fingertips and nose turns blue bc of RBC agglutination

Warm IgG:
Extra vasc
No plasma hgb
No urine hemosiderin
Low haptoglobin
Gamma Coombs' POSITIVE
Non-gamma Coombs' pos/neg
Acrocyanosis neg

Keep patient warm

Note: steroids don't work

Repetitive trauma (marching) to feet/hands results in RBC fragmentation and hematuria.

Aortic valve replacement, if not placed well, RBCs will shear against valve and fragment.

IgG (warm auto-ab) coated RBCs get pitted out (sphere shape) by spleen with repeated passes

Small BV anemia--RBCs destroyed in tiny BVs

Inc'd fibrinogen turnover, deposition of fibrin in arterioles, shearing of RBCs

Assocd with TTP (Thrombotic thrombocytopenic purpura) and DIC (Disseminated intravascular coagulation: pathologic acceleration of clotting cascade)