Pathology Student

Q. In liver cirrhosis, why is the PTT not elevated? In all of my review books, it says the PT is used as one of the ways to evaluate liver function. But it seems like the PTT should also be elevated!

A. Both the PT and the PTT can be prolonged in liver failure. The liver makes most of the coagulation factors – including the factors in both the intrinsic and extrinsic pathways. So both the PT (which assesses the extrinsic pathway) and the PTT (which assesses the intrinsic pathway) will be prolonged if the liver is not making coagulation factors like it should.

When you’re using coagulation tests to monitor liver failure, the PT may be a better test than the PTT. The PT assesses factor VII, which is the coagulation factor with the shortest half-life. So the first test to become abnormal if you stop making coagulation factors is the PT; then later, as the other coagulation factors start to become noticeably less abundant, the PTT becomes prolonged too. Perhaps that’s why board review books focus more on the PT (rather than the PTT) in this context.

The same principle holds for people on coumadin. Coumadin affects all the vitamin K dependant coagulation factors (II, VII, IX, X), so eventually, if you’re on a big enough dose, you’ll end up with both a prolonged PT and a prolonged PTT. Usually, though, you use the PT to follow someone as you’re adjusting their coumadin dose, because it’s more sensitive (it will become prolonged before the PTT). That’s important, because when someone is on coumadin, you want to anticoagulate them a little, but not too much. If you only used the PTT, you wouldn’t see an abnormality until factors IX and X dropped below normal levels - and by then the patient would be severely anticoagulated.

Bottom line: you are absolutely correct - both PT and PTT can be prolonged in liver failure.

The image of a cirrhotic liver above is from Wikimedia commons (http://commons.wikimedia.org/wiki/File:Cirrhosis_high_mag.jpg).

Okay, so this post is more about being a student than it is about the study of pathology. Bear with me: there is important information here!

Of the two hormones produced by the posterior pituitary (oxytocin and antidiuretic hormone), the more interesting by far is oxytocin. Called the “cuddle hormone,” it has been shown to mediate trust, connection, monogamy, and basically any other good emotion that occurs in relationship with others. On Tuesday, the New York Times published an article entitled “Evidence That Little Touches Do Mean So Much” which suggests that oxytocin has another very important effect that may have implications for students in classrooms.

The article talks at length about research showing how small, physical interactions (a touch on the arm, a high-five, etc.) have a positive effect on both the toucher and the touchee. Some of the positive effects are what you’d expect: small touches have been shown to ease pain, soothe depression, deepen a relationship. But here’s something interesting: small touches can also improve performance! A soon-to-be-published study of professional basketball players came to this startling conclusion:

“Players who made contact with teammates most consistently and longest tended to rate highest on measures of performance, and the teams with those players seemed to get the most out of their talent.”

It probably has to do with – you guessed it – oxytocin. The article states: “If a high five or an equivalent can in fact enhance performance, on the field or in the office, that may be because it reduces stress. A warm touch seems to set off the release of oxytocin, a hormone that helps create a sensation of trust, and to reduce levels of the stress hormone cortisol.”

How could oxytocin (a “relationship” hormone) have anything to do with personal performance? The article offers an interesting suggestion:

“In the brain, prefrontal areas, which help regulate emotion, can relax, freeing them for another of their primary purposes: problem solving. In effect, the body interprets a supportive touch as ‘I’ll share the load.’”

So: let’s see more high-fives, more touches on the arm, more secret handshakes. It can’t hurt – especially around exam time!

Image credit: Carina Ice (http://www.flickr.com/photos/carinaice/4089444469/), under cc license

Today’s post, authored by a very smart guest cytogeneticist, nicely describes array-based comparative genomic hybridization, a very cool new DNA test that gives us a way to detect genetic abnormalities that are too small to be seen under the microscope. A student wanted to know more about why array CGH can only detect unbalanced rearrangements (like deletions) but not balanced rearrangements (like inversions).

Q. With regard to array CGH, I do not understand why balanced rearrangements could not be detected. Why can’t they make a probe for an inversion of a few genes or an insertion of a gene? I guess I do not see how these would be any different from making a probe for a deletion or duplication. I am sure I am missing something though.

A. Array-based CGH is a DNA based test that, in a much-simplified nutshell, looks at the quantity of DNA in a patient vs the quantity of DNA in a specimen derived from a pool of normal controls. Thousands of different probes from loci spanning the genome are present on a chip. If there is LESS DNA in the patient than the control for a particular probe, the a-CGH will show a DELETION of material from the patient for that particular locus; if there is MORE DNA in the patient than the control for a particular probe, the a-CGH will show a GAIN of material from the patient for that locus. In a balanced translocation, there is NO gain or loss of material, so the probes will show that the patient and the control have equal amounts of DNA in those translocated regions.

To detect a translocation, then, one would need to do a G-banded chromosomal analysis (i.e, look at the chromosomes under the microscope, the “old-fashioned” way). In that way, the material exchanged between the chromosomes involved in the translocation could be identified because they would LOOK different than their normal homologs — but because the translocation is balanced, there is NO gain or loss of DNA in this exchange, so array-CGH would not detect any genetic imbalance. In cancer cases, in which the genetic abnormalities involved in certain translocations have been well characterized (e.g., the 9;22 translocation in chronic myeloid leukemia involves breakage and rejoining of the ABL gene on chromosome 9q34 and the BCR gene on chromosome 22q11.2), FISH probes can be developed because we know the gene sequences of ABL and BCR. In contrast, however, for a constitutional balanced translocation that is passed on through a family or develops de novo in a patient, we don’t know what those genes are — so we don’t know the base-pair sequences that would enable us to develop a FISH probe. For these cases, then, we are limited to characterizing the abnormality as best we can by means of a G-banded chromosomal analysis.

At the risk of complicating this picture, I will add one further little scenario. Not all translocations that LOOK balanced in a G-banded chromosomal analysis really ARE balanced at the level of the DNA sequences. That is, in the process of formation of the translocation, sometimes very small amounts of DNA can be gained or duplicated at the breakpoints of the translocation. These amounts of DNA are way too small to be detected under the microscope in a G-banded chromosomal analysis (remember, the limit of detection for our eyes at the microscope is about 3 megabases of DNA (i.e. 3 million base pairs)). Gains or losses of DNA at the breakpoint of these apparently balanced translocations that are SMALLER than about 3 MB would NOT be detected in a G-banded chromosomal analysis. For this reason, if a patient is diagnosed with a de novo (not inherited from the parents) translocation that LOOKS balanced under the microscope (via a G-banded chromosomal analysis), we would still recommend that a-CGH be performed — because a-CGH would be able to detect any such small imbalances at the breakpoints of the translocation.

Image credit: DNA spiral by Charles Jencks, Kew Gardens, UK (by mira66, http://www.flickr.com/photos/21804434@N02/3707633630/, under CC license).

Q. In one of my other courses, the professor was discussing hemophilia. He states that the prothrombin time (PT) is normal, the partial thromboplastin time (PTT) is abnormal, the bleeding time is normal, and patients will not have petechiae. I was wondering how there can be no petechiae and a normal bleeding time in a patient with hemophilia. Is it because they still have an intact extrinsic pathway that can get the job done? How do we ever classify or detect these patients in the first place, if they don’t have the classic signs? Thanks!

A. Great questions! In hemophilia A, the problem is that you don’t have factor VIII. In hemophilia B, you don’t have factor IX. The PT (INR) measures the extrinsic arm of the coagulation cascade (the part of the cascade involving factor VII and tissue factor). Since factors VIII and IX are not involved in that arm of the cascade, the PT is normal in patients with hemophilia.

The PTT measures the intrinsic arm of the coagulation cascade (the part of the cascade involving VIII, IX, and a bunch of other factors). The PTT will be abnormal (prolonged) in patients with hemophilia because they lack factors on this side of the cascade.

The bleeding time is interesting. It measures only the response of platelets to a vascular injury. It has nothing to do with the coagulation cascade! Weird, huh?! If you look here, there is a description of why this is the case. So: in patients with hemophilia, the bleeding time will be normal.

Finally: patients with hemophilia have what is called “factor bleeding” (big, destructive bleeds, usually in joint spaces). Petechiae are more characteristic of “platelet bleeding.” Platelet bleeding occurs in diseases like von Willebrand’s disease and various rare intrinsic platelet abnormalities. It is more of a mucosal type of bleeding (petechiae, nosebleeds, heavy periods).

To diagnose a patient with hemophilia, you’d probably first notice that they have an abnormal pattern of bleeding. Maybe after they fall, they get these huge bleeds (with hemophilia, there is usually a memorable preceding incident). To start the work up, you’d do some common lab tests: the PT (INR) would be normal, the PTT would be prolonged, a PTT mixing study (where you mix in some normal blood and run the PTT again) would show a corrected (normal) PTT, and the bleeding time would be normal. You’d suspect hemophilia at this point, and you’d run further tests, including factor VIII and factor IX levels, and genetic tests looking for the gene mutation in hemophilia A and B.

The image above is of Queen Victoria, who passed hemophilia through her children and into the royal families of Spain, Germany, and Russia.

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