Pathology Student

Q. I have been trying to figure out the two basic thyroid lab tests, TSH and T4. If you have a high TSH and a low T4 does that mean that the pituitary gland is going crazy to reach homeostasis but the thyroid is not responding? And inversely, if the T4 is high and the TSH is low does that mean for some reason the thyroid is working overtime due to a disease like Graves disease, and the pituitary is trying to compensate by not producing TSH?

A. Yes! That’s exactly right. When the two (TSH and T4) are opposite of each other – high T4/low TSH or low T4/high TSH – that means that the problem is intrinsic to the thyroid gland (Graves disease or Hashimoto thyroiditis, for example) and the pituitary is trying to control the thyroid by producing more or less TSH. Those are the most common types of thyroid disease – those that are intrinsic, or primary to the thyroid gland itself.

On the other hand, if both TSH and T4 are either low or high – high T4/high TSH or low T4/low TSH – that means that the process is being driven by TSH. Either there’s a pituitary adenoma making a ton of TSH, or the pituitary is not working well for whatever reason (it’s been radiated, or has undergone necrosis) and it’s not making enough TSH.

Image credit: akay (http://www.flickr.com/photos/akay/245002004/), under cc license.

We were talking about developmental pathology the other day in class – trisomies, sex chromosome numerical abnormalities, microdeletion syndromes etc. – and the term “uniparental disomy” came up. Someone asked, what is that, and how do you get it? Great question! Before we get to the answer, let’s take a look at some of the syndromes that are caused by this abnormality.

The most well-known syndromes caused by uniparental disomy are Prader-Willi and Angelman syndromes. These are both microdeletion syndromes, meaning that the patient has a little deletion within a chromosome that is so tiny that it is often not visible by regular G-banding techniques (you need to use FISH).  Both Prader-Willi and Angelman syndromes are caused by tiny deletions in chromosome 15. The interesting thing is that if the deletion is in dad’s chromosome 15, the baby develops Prader-Willi syndrome, but if the deletion is in mom’s chromosome 15, the baby develops Angelman syndrome. Patients with these syndromes have uniparental disomy, meaning that they have inherited both copies of the abnormal chromosome 15 from one parent (instead of one from mom and one from dad). We’ll discuss how this can happen in a minute.

The two syndromes are surprisingly different. Patients with Angelman syndrome have mental retardation, a jerky, puppet-like gait, inappropriate outbursts of laughter, and severe speech problems. Patients with Prader-Willi syndrome have poor muscle tone and poor feeding as babies, but later develop an obsession with food, resulting in extreme food-seeking behavior and obesity.

Back to the question. Uniparental disomy means that you inherit two copies of a particular chromosome from one of your parents, and no copy from the other parent. It can happen in three ways, all of which involve two consecutive mistakes in cell division.

1. Trisomic rescue. This happens when you get a trisomy (as happens when the chromosomes don’t split up the way they should during meiosis, and you end up with two copies of some chromosome from mom and one from dad – or vice versa), and then you lose one of those three chromosomes (the “odd one out”, the lone one from one of the parents). You’re left with two chromosomes from one parent, and none from the other.

2. Monosomic rescue. This happens when you have a monosomic zygote (only one copy of a particular chromosome – the other parent’s dropped out), and that chromosome duplicates itself.

3. Gamete complementation. This is when you have a gamete with two copies of a chromosome (should have only one), and it gets fertilized with a gamete that happens to have no copies of that chromosome.

Here’s a good reference with diagrams. The more I read about this stuff, the more amazed I am that things usually go right.

The image above is “Boy with a Puppet” or “A child with a drawing” by Giovanni Francesco Caroto. Dr. Harry Angelman, a pediatrician working in England, first reported three children with what is now known as Angelman syndrome in 1965. While vacationing in Italy, Angelman saw the painting.  The boy’s laughing face reminded him of his three patients, as did the puppet in the drawing, which reminded him of the fact that all three patients exhibited jerky movements. He subsequently described the children with this syndrome as “puppet children,” a title that was obviously not very pleasing. The name of the syndrome was later changed to Angelman syndrome.

Pathology Student is back after a nice long holiday hiatus. We will begin 2010 with a new series of real live questions from real live students. It is important to hear other students’ questions (and answers) because 1) you will probably learn or clarify something, and 2) it will hopefully encourage you to ask your own questions. So, without further ado, here are some questions and answers about female reproductive system pathology.

Q. In endometriosis, is the glandular tissue found outside of the uterus and not associated with it at all other than being of similar cellular makeup? In other words, is it essentially extra-uterine menses?
A. Endometriosis is extra-uterine endometrial tissue, not associated with the stuff inside the uterus at all – other than it is under the same hormonal control, so when the endometrial tissue inside the uterus undergoes cyclic changes, so will the endometrial tissue (endometriosis) outside the uterus.

Q. Is nulliparity a risk factor in endometrial hyperplasia?
A. Yes, actually, it is, although our textbook [Robbins Basic Pathology] doesn’t mention it. It falls into the category of things-that-increase-estrogen-exposure, so it’s a risk factor for any of the tumors related to estrogen excess.

Q. The risk factors for endometrial hyperplasia include exogenous hormone use. Is this the same thing as estrogen replacement therapy?
A. In this setting, yes, they are the same thing.  If you want to be complete about it, there are other kinds of exogenous hormones – like birth control pills – but when we’re talking about endometrial hyperplasia, the exogenous hormomes referred to are estrogen replacement therapy (birth control pills don’t have that effect on the endometrium).

Q. It seems like too much estrogen causes a bunch of issues. Do many of these pathologies arise simultaneously in the presence of excess estrogen?
A. No, not usually. The chances of any one tumor or lesion arising are relatively small (even though the risk is increased compared to the setting of normal estrogen), so the chances of two developing at the same time are very small.

Q. Can you give an example of what metrorrhagia is and when it might take place?
A. Metrorrhagia means there is bleeding outside the normal period time, for example: abnormally-timed bleeding during menopause, or bleeding from an intra-uterine tumor (which would not follow normal hormonal stimuli).

Q. Could a teratoma be an ectopic pregnancy?
A. No – a teratoma is a neoplasm; it is monoclonal. It arises from a germ cell that has gone bad and decided to develop into all three germ cell layers. The cells may grow to look like normal tissues, but they’re not under any embryologic organization or control (they just grow haphazardly). A pregnancy, whether it is intrauterine or extrauterine, is not monoclonal; the tissues are growing in response to embryologic signals, and if left alone, will organize into a human.

Q. What is peau d’orange?
A. Peau d’orange (French for “skin of the orange”) happens when you have a breast cancer that has infiltrated the lymphatics of the breast skin, making the skin edematous and orange-peel-looking. This change often happens in inflammatory breast cancer (so-named because the skin can look inflamed), in which the tumor preferentially involves lymphatics.

Q. My 28 year old friend was just diagnosed with multiple sclerosis. What can he expect regarding prognosis?

A. MS is a demyelinating disease that is thought to be autoimmune in nature. It is not easy to predict an exact prognosis for an individual patient, but I think you can boil it down to the fact that while a small number of people with MS become unable to write, speak, or walk, the vast majority of patients are mildly affected by their disease. Let’s look at this in a little more detail.

Subtypes

There are several subtypes of MS, each with different symptoms and prognoses. Note that the frequencies of the different subtypes listed in different sources may not be comparable, because some sources refer to the frequency at diagnosis, while others refer to an overall frequency. It would be useful to know which subtype your friend fits into, because that may help determine his prognosis.

1. Benign MS
People with this type of MS have only rare attacks, and are minimally disabled 10 years after their diagnosis (therefore, you can’t make this diagnosis until 10 years have elapsed!).

2. Relapsing-Remitting
People with this type of MS attacks followed by partial or complete recovery periods free of disease progression. This is the most common type at diagnosis – but some patients move into one of the other types later on.

2. Primary-Progressive
People with this type of MS experience a slow but nearly continuous worsening of their disease from the onset, with no distinct relapses or remissions. This is an uncommon subtype.

3. Secondary-Progressive
People with this type of MS experience an initial period of relapsing-remitting MS, followed by a steadily worsening disease course. Many people with relapsing-remitting MS developed this form later on – but that was before new drugs for MS were introduced. This subtype may be less frequent now.

4. Progressive-Relapsing
People with this type of MS experience a steadily worsening disease from the onset but also have relapses, with or without recovery. In contrast to relapsing-remitting MS, the periods between relapses are characterized by continuing disease progression. This is an uncommon subtype.

Factors influencing prognosis

1. Factors associated with a better prognosis:

• female gender
• age of disease onset earlier than 40 years
• a first attack consisting of optic neuritis or other sensory symptoms
• lack of significant disability 5 years after onset
• minor abnormalities on brain MRI scan at the time of diagnosis.

2. Factors associated with a less favorable prognosis:

• male gender
• age of onset at age 40 or later
• a first attack consisting only of motor symptoms
• difficulty walking or sustained impairment in coordination after resolution of first attack
• large number of MRI lesions

All that being said…

It’s going to be hard to tell with a lot of certainty at this point what your friend’s prognosis is, because the diagnosis is new. Once he has had the disease a few years, then it will be important to see how it has progressed (or not progressed), because one of the more important predictors of one’s future MS course is one’s past MS course.

Here are some good web resources for learning more about MS:

1. The NIH
http://www.ninds.nih.gov/disorders/multiple_sclerosis/multiple_sclerosis.htm

2. The National Multiple Sclerosis Society
http://www.nationalmssociety.org/index.aspx

3. The University of California – San Francisco Multiple Sclerosis Center
http://www.ucsf.edu/msc/faq.htm#beyond

4. The Multiple Sclerosis International Federation
http://www.msif.org/en/about_ms/types_of_ms.html

The illustration above is from Joseph Babinski’s 1885 thesis, “Etude anatomique et clinique de la sclérose en plaques.”

Here are some real student questions about myeloproliferative disorders. You should always ask questions when you don’t understand something – preferably in lecture. If you don’t understand something, at least 5 other people are having the same problem.

Q. Can chronic myelofibrosis lead to anemia?

A. Yes! It can lead to anemia because the marrow eventually get so full of fibrosis that there is no room for the red cells (and all the other cell types) to grow. The cells try their best to grow elsewhere, but it’s never as good – and patients eventually get anemic.

Q. With polycythemia vera, are both the bone marrow and blood full of red cells?

A. Yes! In polycythemia vera, there is a panmyelosis (like in all myeloproliferative disorders), but the line that’s dominant is the red cell line. The marrow is stuffed with them, and they spill out into the blood as mature red cells. The RBC goes way up, and the blood gets more viscous and sludgy. One way to treat these patients is to do periodic phlebotomy to get rid of the excess red cells.

Q. In essential thrombocythemia, are there an increased number of megakaryocytes seen in marrow and blood too? Do megakaryocytes escape the marrow since there is a malignant proliferation?

A. Yes, there is an increased number of megakaryocytes in the marrow! They end up making a TON of platelets, which spill into the blood. The megakaryocytes do not spill into the blood because they are HUGE – too big to get out.

Q. Would essential thrombocythemia be considered an underlaying cause of DIC? Is the high count of platelets consistent or does it fluctuate?

A. Essential thrombocythemia is not considered a cause of DIC. There are definitely a ton of platelets around – and sometimes they can sludge up into little vessels – but they don’t really initiate the coagulation cascade, like DIC does (in DIC, the problem is not only that you have platelet clots all over, but you’re sealing them up with fibrin. When the red cells try to go through, they get snagged on the fibrin strands). The high count remains pretty consistently high, unless you treat the patient. By the way, patients with essential thrombocythemia can either have abnormal clotting or abnormal bleeding (they can actually develop a secondary (or “acquired”) von Willebrand disease! Weird! So can some of the other myeloproliferative disorders.).

Q. Are chronic myeloproliferative disorders incurable?

A. All chronic leukemias – myeloproliferative disorders and lymphoproliferative disorders – tend to be slowly-progressing, incurable disorders. The exception is chronic myeloid leukemia, which is a relatively (compared to the other chronic leukemias) faster-progressing disorder. It also has a really, really good treatment now – a drug called imatinib (or Gleevec) that can essentially halt the progression of the disease. It doesn’t really ”cure” CML, but it does turn it into a chronic disease that people can live with for many many years.

Image credit: Stefan Baudy (http://www.flickr.com/photos/-bast-/349497988/)

Here’s a little quiz on anemia. Answers are in the first comment following this post.

1. Which of the following is a sign of red cell destruction?

A. ↑ haptoglobin
B. ↓ LDH
C. ↑ bilirubin
D. ↑ reticulocytes
E. ↑ LAP

2. Your patient is a 68 year old male who has very pale, almost bluish fingertips. When you question him about this, he says that it gets worse when he’s out in the cold, and that his doctor says he has some kind of anemia.

Which of the following is probably true?

A.He is making IgG antibodies against his red cells
B. His DAT would be negative
C. The spleen is the major site of red cell destruction in this patient
D. His blood smear would show schistocytes
E. Complement is attacking his red cells

3. What is the defect in hereditary spherocytosis?

A. A point mutation in a hemoglobin chain gene
B. Absence of one or more hemoglobin chain genes
C. Absence of a red cell enzyme
D. A spectrin abnormality
E. Inability to incorporate iron into hemoglobin

4. Your apparently healthy, 75-year-old grandfather was found to have an abnormality on his blood smear during a routine physical. His indices are as follows:

Hgb  8 g/dL (12-16)
MCV 70 fL(80-100)
RDW 15% (12 – 13.5)
RBC 3.5 x 10^12/L (4.5-6.0)
WBC 10 x 10^9/L (4-11)
Plt 300 x 10^9/L (150-450)

What should be done next?

A. Check his blood smear at his next annual physical
B. Give him iron replacement
C. Perform a complete physical, including testing for blood in the stool
D. Give him steroids
E. Do a bone marrow biopsy

5. Your next patient, a 65 year old Finnish bachelor, is a self-proclaimed heavy drinker. He has the following indices:

Hgb  8 g/dL (12-16)
MCV 110 fL(80-100)
RDW 13% (12 – 13.5)
RBC 3.5 x 10^12/L (4.5-6.0)
WBC 7.2 x 10^9/L (4-11)
Plt 420 x 10^9/L (150-450)

What is the most likely diagnosis?

A. Iron-deficiency anemia
B. Thalassemia
C. Megaloblastic anemia
D. Hereditary spherocytosis
E. Sickle cell anemia

Another quiz – this time on acute leukemia. Answers and explanations are in the first comment following this post.

1. Patients with which of the following leukemias may go into DIC if given routine chemotherapeutic agents?

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

2. All of the following terms are technically incorrect, EXCEPT:

A. Acute lymphocytic leukemia
B. Chronic myeloblastic leukemia
C. Chronic lymphoid leukemia
D. Leukemoid reaction
E. Chronic myeloid leukemia

3. Which of the following leukemias is likely to show a panmyelosis:

A. Acute lymphoblastic leukemia
B. Acute monoblastic leukemia
C. Acute erythroblastic leukemia
D. Chronic lymphocytic leukemia
E. Chronic myeloid leukemia

4. A bone marrow biopsy shows 5% myeloblasts and some funny-looking neutrophils and precursors. The most likely diagnosis is:

A. Acute myeloid leukemia
B. Acute lymphoblastic leukemia
C. Myelodysplastic syndrome
D. Bacterial infection
E. Chronic myeloid leukemia

5. While looking around a blood smear, you notice a blast with an Auer rod in it. This patient has:

A. A bacterial infection
B. No disease, unless 20% of the nucleated cells have Auer rods
C. A myelodysplastic syndrome
D. Acute myeloid leukemia
E. Acute lymphoblastic leukemia

6. Acute lymphoblastic leukemia:

A. Often has a good prognosis
B. Never occurs in children
C. Is classified according to morphologic appearance
D. Is only diagnosed when 20% or more of the nucleated cells are lymphoblasts
E. Is an indolent disease

7. Which of the following is a GOOD prognostic indicator in acute lymphoblastic leukemia?

A. Age less than 1
B. A WBC >10,000
C. B-lineage immunophenotype
D. Normal cytogenetics
E. Age >10

Here’s a little coagulation quiz to start your morning. Answers and explanations are in the first comment following this post.

1. Which of the following initiates the coagulation cascade IN VIVO?

A. Factor XII
B. Thrombin
C. Tissue factor
D. Factor X
E. Prekallikrein

2. What does von Willebrand factor do?

A. Binds platelets to each other
B. Binds platelets to the subendothelium
C. Binds platelets to the phospholipid surface
D. Carries factor VII
E. Cleaves factor V

3. Which of the following is true?

A. The intrinsic system is activated first, and then the extrinsic system is turned on later
B. The extrinsic system is weak and short-lived
C. The extrinsic system is only important in vitro
D. Factors V and VII are only important in vitro

4. Which of the following anti-clotting substances acts on factors V and VIII?

A. ATIII
B. Protein C
C. TFPI
D. Plasmin
E. t-PA

5. Which of the following is a cofactor?

A. XII
B. X
C. VIII
D. VII
E. II

6. What are the ingredients in a PTT?

A.  Plasma + phospholipid
B. Plasma + thromboplastin
C. Plasma + calcium
D. Plasma + thrombin
E. Plasma + plasmin

7. Which test evaluates the extrinsic pathway?

A. PT (INR)
B. PTT
C. TT
D. Closure time
E. Bleeding time

8. Which of the following is true regarding the bleeding time?

A. It is a highly reliable and reproducible test
B. The sample is evaluated using an optical densitometer
C. It evaluates platelet function in vivo
D. It is a commonly ordered test
E. It evaluates the coagulation system

9. What is the most common inherited bleeding disorder?

A. von Willebrand’s disease
B. Hemophilia A
C. Hemophilia B
D. Factor V Leiden
E. TTP

10. Which disorders may show “factor-type” bleeding?

A. von Willebrand’s disease
B. Hemophilia A
C. Both
D. Neither

11. Patients with which of the following diseases always have a normal PTT?

A. von Willebrand’s disease
B. Hemophilia A
C. Hemophilia B
D. Factor V Leiden

12. TTP:

A. May present with CNS deficits
B. Is caused by a toxin produced by E. coli
C. Is treated supportively
D. Does not show a microangiopathic blood picture

The gorgeous photo of Leiden (as in Factor V Leiden) was taken by Motumboe (http://www.flickr.com/photos/motumboe/2709667509/).

Q. I have a question about forming the platelet plug. Where are the phospholipids that get exposed, and how does platelet aggregation affect that? If this is in the subendothelium why weren’t they exposed upon ripping or whatever caused the endothelial damage? Also, what is tissue factor?

A. The phospholipids you’re referring to are part of the platelet cell membrane. The platelet membrane contains many different kinds of phospholipids on its surface. This is important because many of the coagulation factors (for example, the factor Xa-Va complex) require a phospholipid surface to exert their effects. During platelet aggregation, some of the phospholipids undergo important changes, making them more available to the coagulation factors.

Here is how a platelet plug is formed:

1. The endothelium gets ripped up, which exposes subendothelial proteins (like collagen) to the blood.

2. The platelets see these subendothelial proteins, and they stick to them using von Willebrand factor (this step is called platelet adhesion).

3. As the platelets adhese, they flatten out and release their granules (which have a lot of functions, one of which is to attract other platelets).

4. Other platelets come to the adhesion site, and they stick down onto the platelets that are already there (this step is called aggregation).

5. Now the platelet plug is formed. One cool thing about the platelet plug – in addition to its function of plugging the hole in the vessel – is that the platelet membrane provides a phospholipid surface which is essential for many of the coagulation factors. In fact, when platelets aggregate, certain phospholipids in their membranes become even more available to be used by the coagulation factors.

Tissue factor is a separate thing. It is the substance that initiates the whole coagulation cascade in vivo. It’s present in different areas of the body (in the subendothelium, in some inflammatory cells, and perhaps even in little locked-up microparticles in the blood). It is not present in active form in the blood until it’s needed for coagulation. So when the endothelium is ripped up (or when inflammatory cells decide to release it, or when the little microparticles get a signal to open up), tissue factor is exposed to the blood, and it binds to factor VIIa, and the cascade proceeds along the extrinsic pathway.

A different kind of plug: the image of Claes Oldenberg’s giant three-way plug at the Tate was taken by jovike (http://www.flickr.com/photos/49503078599@N01/54082836/), under cc license.

Q. Could you explain the “defect in spectrin” in hereditary spherocytosis—how does this cause cells to become spherocytes?

A. Several mutations have been described in hereditary spherocytosis, each with a slightly different spectrin defect. In all of the mutations, though, there is a problem with the connection between spectrin (a long heterodimer situated just inside the cell membrane) and the cell membrane itself. The cell membrane becomes unstable, and as a result, bits of membrane are lost (but the volume inside the red cell remains intact). When you lose membrane, but keep the cell contents intact, the cell starts to “round up”, and instead of being a biconcave disk, it turns into a ball, or spherocyte. Spherocytes are inherently more fragile than regular old biconcave-disk-shaped red cells. They also are less able to maneuver through tight spaces. So they are more likely to break, causing a hemolytic anemia.

Q. In microangiopathic hemolytic anemia, how does clot formation cause red cells to get “ripped” up? Is it because they have less room to maneuver through the vessel? Also, could you give me an example of an obstetric complication that would cause this anemia?

A. When you form a clot, you start by sticking platelets together, and then through a series of enzymatic steps, you make a long polymer called fibrin that sort of cements the platelets together. Sometimes the fibrin strands (especially if you’re forming a lot of them) can ensnare red blood cells as they are flowing through the vessel. The cells get snagged on the strands of fibrin, and they get ripped apart, forming fragmented red cells (schistocytes) that you can see on a blood smear. This is the mechanism for most cases of microangiopathic hemolytic anemia. However, there are some cases that are due to other mechanisms (one example would be a patient with an old-fashioned, ball-and-socket artificial heart valve that smashes a few red cells every time it closes). These cases are less common, and they really aren’t “microangiopathic” since the problem isn’t really in little vessels. But they’re lumped into the same category because they show fragmented red cells.

In some deliveries, especially difficult or traumatic ones, amniotic fluid can leak into the mother’s blood. Amniotic fluid has procoagulant substances in it that kick off the coagulation cascade (the part of clot formation in which you make fibrin). If you’re making lots of fibrin, chances are the red cells are going to get trapped in the fibrin strands, as described above.

Q. In autoimmune hemolytic anemia, I am confused with the warm and cold types. Does IgG stick better to cells in warm temperatures and IgM in cold? How does agglutination cause anemia? Is it because there are less red cells to circulate freely?

A. Some antibodies tend to stick better to red cells at warm temperatures, and some tend to stick better at cold temperatures. You’re right; for some reason, the antibodies that bind better at warm temperatures tend to be IgG, where as the cold-binding antibodies tend to be IgM.

In cold autoimmune hemolytic anemia, there are two things going on:

1) IgM sticks to the red cells at cold temperatures (like in blood in the fingers and earlobes), where it agglutinates red cells and forms big clumps. This doesn’t cause anemia, and it doesn’t really do much damage – it usually just causes some decreased blood flow to these regions (the agglutination goes away when you warm up those body parts).

2) Complement binds to the red cells (why this happens in cold, but not warm, autoimmune hemolytic anemia, nobody knows). This is bad. Complement pokes holes in the red cells, causing hemolysis. So this is what leads to the anemia – not the agglutination.

In warm autoimmune hemolytic anemia, the anemia is due to macrophages either 1) totally engulfing the IgG-coated red cells (and thus removing them from the circulation), or 2) chewing off bits of membrane (and thus turning the red cell into a spherocytes, which is more fragile than a regular red cell).

Q. Why is LDH increased in hemolytic anemia?

A. Lactate dehydrogenase (LDH) is an enzyme that is present in lots of cells in the body: heart, lung, kidney, liver, muscle, and red blood cells. It’s also present in some tumor cells. Any time these cells are destroyed, LDH is released, and you can measure it in the serum. There are different isozymes (red cells have the LDH-2 isozyme), and you can measure these independently in the serum, so you know where the LDH is coming from.

Image credit: Eleaf (http://www.flickr.com/photos/eleaf/2536358399/), under cc license.