Autoimmune hemolytic anemias
Warm reacting antibodies are IgG and cold reacting is IgM
MC autoimmune hemolytic anemia = warm; MCC of it = Lupus
When you have autoimmune dz in your family, you have certain HLA types that predispose you to
that autoimmune dz. Therefore, you should not be surprised if you have one autoimmune dz you’re
likely to have another. So, pts with lupus commonly also have autoimmune hemolytic anemia,
autoimmune thrombocytopenia, autoimmune neutropenia, and autoimmune lymphopenia.
For example: the MCC of hypothyroidism = hashimoto’s thyroiditis; these pts commonly have other
autoimmune dz’s – ie pernicious anemia, vitiligo, autoimmune destruction of melanocytes). So, if
you have one autoimmune dz, you are likely to have others (ie if you have a hemolytic prob, it is
prob autoimmune related).
This is b/c of the HLA relationship. Therefore, if you have a family that has an autoimmune dz, what
would be the single best screening test to use? HLA (ie if they have the HLA type specific for lupus –
there are specific HLA’s for diff dz’s). Therefore, HLA is the best way to see if pt is predisposed to
MCC autoimmune anemia = Lupus; it has IgG and C3b on the surface of the RBC, so it will be
removed by the macrophage. This is an extravascular hemolytic anemia. How do we know that
there are IgG or C3b Ab’s on the surface? Direct Coomb’s test: detect DIRECTLY the presence of IgG
and/or C3b on the surface of RBC’s. Indirect coombs is what the women get, when they are
pregnant and they do an Ab screen on you (looking for any kind of Ab); so, when you look for Ab in
the serum (NOT on RBC, on SERUM), this is an indirect Coombs. Therefore, another name for the
indirect Coombs = Ab screen; with direct coombs, we are detecting IgG and/or C3b on the SURFACE
of RBC’s. you cannot do direct coomb’s on platelets or neutrophils, but only RBC’s.
So, the test of choice if you suspect an autoimmune hemolytic anemia is Coomb’s test.
Drug induced autoimmune hemolytic anemias:
There are 3 types of drug induced hemolytic anemia (2 MCC autoimmune hemolytic anemia =
drug induced; MCC = lupus)
PCN – mechanism: the bpo group of PCN attaches to RBC (lil piece of PCN is attached on RBC
membrane). This is bad if an IgG Ab develops against it b/c if it does, than the IgG attaches
to the bpo group, goes to the spleen and is removed extravascularly; this is an ie of type II
Example: pt on PCN develops a rash – what type of HPY? Type I. Example: Pt on PCN
develops a hemolytic anemia – what type of HPY? Type II
Methyldopa – aka aldomet. Use: anti-HTN for pregnant woman (other anti-HTN used in
pregnancy = hydralazine). Methyldopa and hydralazine have complications – methyldopa
can cause a hemolytic anemia; hydralazine can lead to drug-induced lupus (2 tond
procainamide for drug induced lupus). Methyldopa works differently from PCN: methyldopa
messes with Rh Ag on surface of RBC and alters them. They are altered so much that IgG
Ab’s are made against the Rh Ag (our OWN Rh Ag). So, the drug is not sitting on the
membrane, it just causes formation of IgG Ab’s and they attach to RBC to have macrophage
kill it – what type of HPY is this? Type II. Therefore, methyldopa and PCN are type II for
hemolytic anemia. Quinidine: this is the ‘innocent bystander’ b/c immune complexes are formed. Quinidine
acts as the hapten, and the IgM Ab attaches; so, the drug and IgM are attached together,
circulating in the bloodstream. This is a different HPY – type III, and will die a different way,
b/c this is IgM. When IgM sees the immune complex, it will sit it, and activate the classical
pathway 1-9, leading to intravascular hemolysis, and haptoglobin will be decreased, and in
the urine, Hb will be present.
Microangiopathic hemolytic anemia
RBC’s all fragmented – schistocytes (schisto – means split). MCC chronic intravascular hemolysis =
aortic stenosis, in this dz, the cells hit something; therefore have intravascular hemolysis, Hb in the
urine and haptoglobin is down. This is a chronic intravascular hemolysis, and you will be losing a lot
of Hb in the urine; what does Hb have attached to it? Fe; so what is another potential anemia you
can get from these pts? Fe def anemia. Example: will describe aortic stenosis (systolic ejection
murmur, 2 ICS, radiates to the carotids, S4, increased on expiration, prominent PMI), and they
have the following CBC findings: low MCV, and ‘fragmented’ RBC’s (schistocytes) – this is a
microangiopathic hemolytic anemia related to aortic stenosis.
Other causes of schistocytes: DIC (lil fibrin strands split RBCs right apart b/c RBC is very fragile);
thrombotic thrombocytopenic purpura, HUS – see schistocytes. When you have platelet plugs
everywhere in the body, the RBCs are banging into these things causing schistocytes and
microangiopathic hemolytic anemia. Example: runner’s anemia, esp. long distance you smash RBC’s
as you hit the pavement; very commonly, you go pee and see Hb in it; to prevent, use bathroom b4.
Another cause of hemolytic anemia: malaria – falciparum b/c you have multiple ring forms (gametocyte
(comma shaped and ringed form). It produces a hemolytic anemia, which correlates with the fever. The
fever occurs when the cells rupture (the hemolytic anemia).
Intrinsic vs. Extrinsic Hemolytic anemia:
1. Intrinsic – something wrong with RBC, causing it to hemolyze: such as no spectrin, or not
decay accelerating factor to neutralize complement, no G6PD enzyme in pentose phosphate
shunt, or abnormal Hb (ie HbS). Therefore, something wrong inside the Hb molecule, causing it
2. Extrinsic – nothing wrong with the RBC, just at the wrong place at the wrong time; ie it just
happened to smash into the calcified valve (nothing was wrong with it, until it hit the valve).
Then it will be dreading going to the cords of bilroth with destroy it b/c it has been marked with
IgG and C3b for phagocytosis.
Something intrinsically wrong with the RBC causing it to hemolyze but there’s nothing wrong with
the BM (but something intrinsically wrong with the RBC), and the corrective ret ct is greater than
MAD – MC intrinsic probs
Membrane defect (spherocytosis, paroxysmal nocturnal hemoglobinuria), Abnormal Hb (SC
Deficiency of enzyme (G6PD def). Membrane Defects:
(a) Spherocytosis: do no see a central area of pallor therefore must be a spherocyte and
must be removed extravascularly. Clinically manifest with jaundice from unconjugated
bilirubin. Spectrin defect and AD dz; splenomegaly always seen over a period of time.
Gallbladder (GB) dz is common b/c there is a lot more unconjugated bilirubin presented to
the liver and more conjugation is occurring and more bilirubin is in the bile than usual. So,
whenever you supersaturate anything that is a liquid, you run the risk of forming a stone; if
you supersaturate urine with Ca, you run the risk of getting a Ca stone; if you supersaturate
bile with cholesterol, you will get a cholesterol stone; if you supersaturate with bilirubin,
you will get a Ca-bilirubinate stone. Therefore, pts have GB dz related to gallstone dz and
then do a CBC with normocytic anemia and a corrected ret ct that is elevated, and see
congenital spherocytosis. What’s the diagnostic test? Osmotic fragility – they put these
RBC’s wall to wall in different tonicities of saline, and the RBC’s will pop (therefore have an
increased osmotic fragility).
Rx: splenectomy (need to remove organ that is removing them – they will still be
spherocytes and will not be able to form a biconcave disk).
(b) Paroxysmal Nocturnal Hemoglobinuria = defect in decay accelerating factor. So when
we sleep, we have a mild resp acidosis b/c we breathe slowly (if you have obstructive sleep
apnea, the acidosis is worse). When you have acidosis that predisposes the complement
that’s sitting on ALL cells circulating in pe