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 3%.

MAD – MC intrinsic probs

Membrane defect (spherocytosis, paroxysmal nocturnal hemoglobinuria), Abnormal Hb (SC trait Dz),

Deficiency of enzyme (G6PD def).

1. 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 peripheral blood. RBCs, WBCs, and platelets all have complement sitting on it. There is no complement destruction of these cells b/c in our membranes we have delay accelerating factor. This factor causes increased degradation of the complement so it doesn’t have an opp to drill a hole in our membrane, therefore we don’t wake up in the morning with hemoglobinuria, neutropenia and thrombocytopenia. So, if you are missing decay accelerating factor, the complement will be activated and goes from C1-9, leading to intravascular hemolysis. Think about the name (paroxysmal nocturnal hemoglobinuria): occurs at night, and when you wake up in the morning, you pee out hemoglobin. So, when you do a CBC, not only have a severe anemia, but also a neutropenia and a thrombocytopenia: pancytopenia).

2. Abnormal Hb: Sickle Cell Trait/Dz

With sickle cell trait, there is NO anemia and NO sickled cells in the peripheral blood.

You can have sickled cells in a certain part of your body – in the renal medulla within the peritubular capillaries (decreased O2 tension), but not in the peripheral blood. This is b/c in SCDz, the amount of sickled Hb in the RBC determines whether it sickles or not.

Magic # = 60%; if you have 60% or more, HbS can spontaneously sickle. Oxygen tension in the blood also determines whether a cell will sickle or not. At lower O2

tensions, cells are more likely to sickle. This is an auto rec dz, meaning that both parents must have abnormal gene on their c’some (so its 2 traits); therefore, 25% complete normal, 50% heterozygous asymptomatic carrier, 25% complete dz (same with cystic fibrosis).

SC Trait vs. SCDz:

(a) In sickle cell trait, black individual with normal PE and normal CBC, but

microscopic hematuria, the first step is sickle cell screen b/c microscopic hematuria is ALWAYS abnormal and must be worked up but in blacks = 1/8 people have the trait.

So, SC trait is what you are thinking of; not renal stones, or IgA glomerulonephritis, but is SC trait normally.

(b) SCDz – 2 things are happening: Hemolytic anemia (usually extravascular) – can be very severe and commonly requires a transfusion and Occlusion of small BV’s by the sickled cells (blockage of circulation) – lead to vasooclusive crisis, and this ischemia leads to pain. Therefore, they are painful crisis (occur anywhere in the body – lungs, liver, spleen, BM, hands/feet (bactulitis)). Over time, it leads to damage of organs – kidneys, spleen autoinfarcted (autosplenectomy) – in first 10 years of life, pt will have splenomegaly b/c trapped RBC’s, and eventually

autosplenectomy around age 19 (spleen will be the size of a thumb). After 2 years, it is nonfunctional – so even though you have a big/swollen spleen, it isn’t working.

How will you know what that has happened? Howell Jolly body (RBC with a piece of nucleus that should not be in the spleen – if the spleen were working, a fixed

macrophage would have taken care of it). This occurs at about 2 yrs of age. This is fortunate b/c this is about the age where you can get pneumovax. With a

nonfunctional spleen what infection is guaranteed? Strep pneumoniae sepsis.

MCC death in child with SCDz = strep pneumoniae sepsis.

They try to cover with antibiotics and pneumovax – pneumovax can be given at the age of 2 and that’s about the time when the spleen stops working (start to see Howell jolly bodies). Slide with Howell jolly body and slide with sickled cells, then will ask, what’s wrong with the spleen? It’s dysfunctional; Howell jolly would have been removed if the spleen is functional.

When do they get their first sickle cell crisis? When little kids gets painful hands, and are swollen up (called bactulitis) – does not occur at birth, b/c HbF inhibits sickling and newborns in newborns, 70-80% of their RBC’s are HbF. In SCDz, 60-70% RBC’s have HbF, while the rest are HbS!

At this stage, there is enough HbF to inhibit the sickling; however, as the RBC’s are broken down and replaced, the HbF decreases and HbS increases, and by 6-9 months of age, there is a high enough concentration to induce sickling and their first

vasooclusive crisis, producing bactulitis. So, bactulitis doesn’t come until 6-9 months b/c HbF inhibits the sickling.

Bone infarctions occur from sickling the BM.

Osteomyelitis – these pts are susceptible to osteomyelitis from salmonella due to a dysfunctional spleen. Salmonella is destroyed by macrophages. The spleen normally filters out salmonella, but is dysfunctional. MCC osteomyelitis is staph, but MCC in SCDz pt = salmonella.

What drug is used to decrease the incidence of vasooclusive crises? Hydroxyurea.

How does it work? It increases HbF synthesis.

3. Deficiency of enzyme: G6PD deficiency G6PD def is X-linked recessive.

Most enzyme def’s are auto recessive ie PKU, albinism, homocystinuria). What are the two X-linked recessive enzyme def’s? G6PD def and Lesch-Nyhan syndrome (involves purine metabolism with mental retardation, self mutilation, increased uric acid, def of HGPRT).

Glucose 6 phosphate has several functions: (1) to make glutathione, (2) to make ribose 5 carbon sugars for making DNA, and (3) to make glycogen from G6P (converted to G1P, UDP-glucose and glycogen).

Key: with this enzyme, we can make NADPH, which is the main factor for making anabolic types of biochemical rxn (ie steroid synthesis). NADPH will reduce oxidized glutathione to glutathione; its job is to neutralize peroxide to water. Which vitamin catalyzes this rxn? Riboflavin. Which enzyme helps glutathione neutralize peroxide?

Glutathione peroxidase. Which trace metal is involved? Selenium. Every living cell makes peroxide as an end product, therefore every cell must a way to handle it.

Catalase – present in all cells except RBC’s and it can neutralize peroxide. It is stored in peroxisomes. Other way to neutralize peroxide is with glutathione (only thing available to RBC’s b/c they don’t have catalase). So, if you are deficient in this enzyme, there is a problem. So, peroxide increases to the point of hemolyzing RBC’s why would that occur?

B/c if you had an Infection, or if you took an oxidizing drug (ie sulfa drug, nitryl drug), which will lead to a lot more peroxide lying around. Peroxide will not be able to be neutralized if you are deficient in catalase. So, what will happen is the peroxide will affect the Hb. The peroxide will cause the Hb to clump and form Heinz bodies (Hb clumped up together). Will also affect the RBC membrane b/c it damages the membrane so much that the primary mechanism of destruction is intravascular. Little element is extravascular, but mostly intravascular. It is precipitated by infections and/or drugs. 2 MC drugs: 1) primaquine– missionary got malaria, received a drug, and 2-3 days later the got hemoglobinuria, chills, and a hemolytic anemia (this is primaquine induced hemolysis). 2) Dapsone is used in treating leprosy; every person with leprosy is given a screen for G6PD def b/c of the high incidence of producing hemolysis. See this dz in the same population as Beta thal – blacks, Greeks, Italians. Slide: smear with actively hemolyzing blood cells – Heinz bodies – when it goes into the cords of bilroth, the macrophage will take a big bite out of it and sometimes, is a small bite out of the membrane, and the cell goes to the peripheral circulation and is called a “bite” cell (RBC with little membrane). Need to do special stains to ID Heinz bodies. In Greeks or

Italians with severe forms of G6PD def, they can eat fava beans which can precipitate an episode (aka favism).

Dx – when you have an acute hemolytic episode, the last thing you want to get a diagnosis is to get an enzyme assay. Why? B/c the only cells that are hemolyzed are the ones missing the enzymes. The ones that have the enzyme are still gonna be there, so you have a normal assay. So, NEVER use enzyme assays for active hemolysis. Need to special stain to ID the Heinz body. When the hemolytic episode is over that’s when the dx is confirmed, this is done with a G6PD assay. Will get a question on G6PD

deficiency, either dapsone related or primaquine related.

X. 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 something.

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.