Anemia | Pathology Student

What’s the difference between Howell-Jolly bodies and Heinz bodies?

Q. Love your website, its helped me remember some super key concepts. (more…)

Making sense out of the RDW

Q. I don’t understand the red cell distribution width (RDW)! The formula is: RDW= (MCV standard deviation/ MCV) x 100. If the standard deviation is a fixed number, why does the RDW increase whether MCV is increased or decreased? I understand that in both iron deficiency and megaloblastic anemia it should be increased cause it shows the volume differentiation but it is mathematically obscure to me.

A. Good question! The standard deviation of the mean actually does change depending on what type of anemia the patient has.

Normally, the cells in our blood are all about the same size. So the standard deviation of the mean is fairly low. Meaning that if our MCV is 90 fL, there might be a few red cells that are 88 or 89, and a few that are 91 or 92, but basically, there’s little deviation from the mean – almost every cell is very close to 90 fL in size.

In some types of anemia, there is a huge variation in the size of the red cells. In iron-deficiency anemia, for example, each new wave of iron-depleted cells is smaller than the last (because there is less and less iron around). So the older red cells are bigger than the newer red cells. If the overall MCV in a particular case is 70 fL, there are going to be some cells (the older ones) that might be close to 80 fL, and other cells (the newest ones) that might be around 60 fL. So the deviation from the mean is large, and the RDW is high.

If you think of it in terms of test scores (a topic we all know well!), it might help. The mean score for the class might be, say 80. But it’s also useful to know if everyone scored right around 80 (meaning that the standard deviation was low), or if there were a wide range of scores from 60 to 100 (meaning that the standard deviation was high). Same thing with a blood smear: if all the red cells are roughly the same size, the standard deviation (and RDW) is low. If there is a wide range of sizes, the standard deviation (and RDW) is high.

By the way, the place that the RDW is most useful (in my humble opinion) is in differentiating between iron-deficiency anemia (IDA) and mild to moderate thalassemia. In IDA, as we just talked about, the RDW is high. In mild-moderate thalassemia, the RDW is not elevated. The cells in mild-moderate thalassemia are all basically the same size – probably because the defect in thalassemia is static (unlike the situation in IDA, where the defect worsens over time, so the cells keep getting smaller and smaller).

How does the Schilling test work?

Q. I don’t think I have a good understanding of the Schilling test. If a patient has B12 in their urine does that mean they are absorbing it? (more…)

Hematopathology Quiz Part 3

Here is the final installment of a really nice quiz one of our readers sent (check out the first and second installments).

This is a quiz recently given to medicine, pediatrics and pathology residents rotating through hematopathology. Give it a try and see how many you get right! Make sure you check out the answers and nice explanations (if I do say so myself) at the end.

1. A 24-year-old female presents with prolonged PTT which did not correct following incubation for 2 hours with control plasma. Which of the following is the most likely diagnosis?

A. Hemophilia A
B. Antiphospholipid antibody syndrome
C. Factor V Leiden
D. Von Willebrand disease

2. A “dry tap” on bone marrow aspiration can be seen in all of the following disorders EXCEPT:

A. Chronic myeloid leukemia
B. Hairy cell leukemia
C. Idiopathic thrombocytopenic purpura
D. Polycythemia vera

3. All-trans-retinoic acid is the treatment of choice for which of the following leukemias?

A. Acute promyelocytic leukemia
B. Acute lymphoblastic leukemia
C. Chronic lymphocytic leukemia
D. Chronic myeloid leukemia

4. Which of the following stains is used for supravital staining of polychromatophilic red cells?

A. New methylene blue
B. Oil red O
C. Leishman stain
D. Masson’s trichrome

5. Giant platelets are seen in:

A. Glanzmann thrombasthenia
B. Bernard-Soulier syndrome
C. von Willebrand disease
D. Thrombotic thrombocytopenic purpura

6. The leukemic cells in large granular lymphocyte leukemia are positive for:

A. CD33
B. CD 117
C. CD56
D. CD34

7. A 65-year-old female presents with fatigue. A blood smear shows abnormal lymphocytes, which are positive for CD5, CD19, and CD20, but negative for CD23. Cytogenetic analysis reveals a t(11;14). What is the diagnosis?

A. Hairy cell leukemia
B. Mantle cell lymphoma
C. Marginal zone lymphoma
D. Chronic lymphocytic leukemia

8. Serum tryptase is elevated in:

A. Hairy cell leukemia
B. Mast cell leukemia
C. T-cell acute lymphoblastic leukemia
D. Biphenotypic leukemia

Scroll down for the answers…

1. B. If you have a prolonged PTT, and you’re wondering what the cause is, one thing you can do is a mixing study, which is what this question is getting at. In a mixing study, you add a little normal plasma to the PTT (along with the patient sample) and then run the PTT again. If it “corrects” (meaning that the PTT is now normal), then it means the patient was missing something that the normal plasma provided (usually the thing that’s missing is factor VIII or IX). If it doesn’t correct (meaning that the PTT is still prolonged), then there is something in the patient sample that is inhibiting the test (usually the thing that’s inhibiting the test is an antiphospholipid antibody). So for the answers to the question: the correct answer is B (since the PTT didn’t correct). In hemophilia A, a mixing study would make the PTT correct, so A is wrong. Patients with factor V Leiden or von Willebrand disease don’t have a prolonged PTT, so C and D are wrong.

2. C. A “dry tap” means that you get the needle in the marrow cavity, and when you pull back on the syringe, no marrow is drawn out. This usually means that there is fibrosis in the marrow, which is something you can see in pretty much any myeloproliferative disorder, particularly in the end stages (so A and D could produce a dry tap). In hairy cell leukemia (B), there are little threads of fibrosis surrounding each hairy cell. It gives the marrow a “chicken-wire” appearance. Patients with ITP (C) don’t have fibrosis in the marrow. The problem in ITP is that the body is attacking its platelets – it has nothing to do with fibrosis in the marrow – so C is correct.

3. A. All-trans-retinoic acid (ATRA) is a treatment that was developed for acute promyelocytic leukemia (APL). In APL, the retinoic acid receptor is screwed up, and the malignant cells get “stuck” in the promyelocyte stage. This is not good, because if you give a patient with APL regular chemotherapy, which tends to bust open cells, you’ll release all the promyelocyte granules (which contain pro-coagulant substances), putting the patient at risk for disseminated intravasular coagulation. ATRA overcomes this maturation block, allowing the malignant promyelocytes to mature into myelocytes, then metamyelocytes, then neutrophils. Then you can give the patient regular chemotherapy without the risk of DIC. ATRA doesn’t work in any of the other leukemias listed, because those leukemias don’t have a problem with the retinoic acid receptor.

4. A. Supravital staining means that you do the stain on liquid (not fixed and dried) blood. Supravital stains are used only in certain settings, like when you’re looking for Heinz bodies, or when you’re counting reticulocytes (polychromatophilic cells). The supravital stain used to stain polychromatophilic cells is new methylene blue (A).

5. B. Both Glanzmann thrombasthenia and Bernard-Soulier syndrome are hereditary platelet disorders in which platelet receptors are deficient or defective, and patients bleed excessively. In Glanzmann, IIb-IIIa is deficient, meaning that the platelets can’t bind fibrinogen very well, which means they can’t aggregate well. In Bernard-Soulier, Ib is abnormal (meaning that platelets can’t bind von Willebrand factor very well, and can’t adhese to the subendothelium very well). It turns out that patients with Bernard-Soulier (but not Glanzmann) have big platelets, too. So B is correct. Big platelets are not seen in von Willebrand disease (C) or TTP (D).

6. C. The lymphocytes in large granular lymphocyte leukemia are T cells. They are typically positive for CD8, CD 16, and CD56 or CD57. CD33 (A) is a marker seen mostly on myeloid cells. CD117 (B) is present on hematopoietic stem and progenitor cells, and CD34 (D) is present on hematopoietic stem cells, endothelial cells, mast cells and some dendritic cells.

7. B. The t(11;14) is characteristic of mantle cell lymphoma, and not of any of the other types of lymphoma listed. Also, mantle cells tend to be CD5, CD19 and CD20 positive, but CD23 negative. The cells of hairy cell leukemia (A), marginal zone lymphoma (C) and CLL (D) have different immunophenotypes.

8. B. Mast cells contain tryptase (which is a serine protease) in their little granules. Hairy cells (A), T-cell ALL (C) cells, and the cells of biphenotypic leukemia (D) are all negative for tryptase.

Hematopathology Quiz Part 2

Here is the second of three installments of a really nice quiz one of our readers sent (the first installment is here, and the third one is here). This is a quiz he recently gave to his residents (from medicine, pediatrics and pathology) rotating through hematopathology. Give it a try and see how many you get right! Make sure you check out the answers and nice explanations (if I do say so myself) at the end.

1. Smudge cells may be seen on the peripheral blood smear in which of the following?

A. Chronic lymphocytic leukemia
B. Chronic myeloid leukemia
C. Acute myeloid leukemia
D. Thalassemia

2. The erythroblasts in acute erythroleukemia (AML- M6) are usually positive for which of the following?

A. PAS
B. CD71
C. CD117
D. All of the above

3. The rare Bombay phenotype is seen in people who have blood type:

A. O
B. A
C. B
D. AB

4. Cryoprecipitate contains which of the following factors?

A. Factor VIII
B. Factor IX
C. Factor II
D. Factor VII

5. The major hematopoietic site in the human embryo is:

A. Spleen
B. Liver
C. Kidney
D. Yolk sac

6. POEMS syndrome includes all of the following EXCEPT:

A. Polyneuropathy
B. Ophthalmopathy
C. M-protein
D. Skin abnormalities

7. The most common class of immunoglobulin produced by the malignant cells in multiple myeloma is:

A. IgA
B. IgD
C. IgG
D. IgM

8. Which of the following is true with respect to hemophilia A?

A. Inheritance is autosomal dominant
B. It is more common in females
C. It never manifests before puberty
D. Patients are deficient in factor VIII

9. The cells of which of the following have a “fried-egg” appearance on bone marrow sections?

A. Hairy cell leukemia
B. Follicular lymphoma
C. Acute promyelocytic leukemia
D. Burkitt’s lymphoma

10. Which of the following immunophenotypic markers is a pan-B-cell marker?

A. CD3
B. CD19
C. CD33
D. CD56

Scroll down for the answers…

1. A. Smudge cells (also called ghost cells or basket cells) are actually damaged lymphocytes rather than a unique type of cell. Lymphocytes are more fragile than myeloid cells (like neutrophils) – so when you make a blood smear in a patient with a lymphoid disorder (like chronic lymphocytic leukemia), there are likely to be a bunch of smudge cells.

2. D. CD71 and CD117 are both erythroid markers. Erythroblasts in AML-M6 will often stain positively with the PAS (periodic acid schiff) stain (which stains glycogen and mucopolysaccharides). Normal erythroblasts are generally not PAS positive though.

3. A. People with the Bombay phenotype don’t make H antigen. What’s H antigen, you say? It is the antigen that you make first, before you create A or B antigens. To make A and B antigens, you start with a protein precursor (sticking out of the red cell membrane). You add fucose to make what’s called the H antigen. Then, if you have the A gene, you add N-acetylgalactosamine to the H antigen, which makes it an A antigen. If you have the B gene, you add galactose to the H antigen, which makes it a B antigen. If you don’t have either A or B (in other words, if you are type O), then you just leave the H antigen as is, and you don’t make either A or B antigens.

So…people with the Bombay phenotype do not make the H antigen (they stop at the protein precursor stage). They therefore don’t make A or B antigens, either (so they are type O). If a person with the Bombay phenotype needs a transfusion, you need to find Bombay blood – because if you give any other type (regular A, B, AB or O), that blood will have some H antigen in it, and the patient will bust open all those donor red cells (not a good thing to have happen!).

4. A. Cryoprecipitate is a plasma product that contains fibrinogen, von Willebrand factor, and factors VIII and XIII.

5. D. Ok, kind of a gimme.

6. B. POEMS is a rare syndrome that includes a plasma cell dyscrasia (usually myeloma) and a bunch of other stuff. The acronym covers some of the main features: polyneuropathy, organomegaly, endocrinopathy or edema, M-protein, and skin abnormalities (including hyperpigmentation and hypertrichosis). There are other potential complications, though – and not every patient with POEMS has all five features.

7. C. The most common class is IgG. The rarest is IgM. Some people argue that an IgM myeloma doesn’t exist; others say that it exists but is super super rare. Either way, if you get a plasma cell thing that expresses IgM, the first thing you should think of is Waldenstrom’s – myeloma would be way, way down on the list.

8. D. In hemophilia A, patients are deficient in factor VIII (in hemophilia B, it’s factor IX that is deficient). Inheritance is X-linked recessive (though up to 30% of cases arise spontaneously!). As any X-linked recessive disorder, it is more common in males. It often manifests in childhood.

9. A. The hairy cells in hairy cell leukemia have been described as having a “fried egg” appearance because they have these long cytoplasmic processes (“hairs”) that push the cells apart from each other. So the little cell nuclei look like the yolks of eggs, with egg whites (cytoplasm) around them.

10. B. CD19 is a marker present on most B cells (so it’s a “pan” B-cell marker). CD3 is a T-cell marker; CD33 is a myeloid cell marker, and CD56 is a natural killer cell marker.