Hereditary hemorrhagic telangiectasia, simplified.

Hereditary hemorrhagic telangiectasia is one of a handful of diseases that I could never really get into my head. I don’t know why, because the name is so descriptive – it tells you exactly what the distinctive features of the disease are.

Maybe it’s because my professors used the older name for this disease – Osler-Weber-Rendu disease – which is about as non-descriptive a name as you can get. Good thing we’re getting away from eponymous disease names. They’re charming, but they make life really hard for students.

Back to hereditary hemorrhagic telangiectasia. Let’s take a closer look at this name – because once you know what the words mean, you’ll understand the disease without having to use brute memorization.

We’ll look at the words out of order, so that the explanation makes sense.

Hereditary: This is an autosomal dominant disorder. For boards (I can’t imagine an exam question on this, but who knows?), you might want to know that the mutated genes in this disorder encode parts of the TGF-ß signaling pathway.

Telangiectasia: This is a great name, because everything you need to know is right there in the name. Too bad we don’t have time to cover some simple Greek and Latin word roots in medical school, because once you know a few, you can easily figure out what words mean. Telangiectasia comes from three Greek words:

  • τέλος (telos), meaning end (For example: telomeres are the little things on the ends of chromosomes.)
  • ἀγγεῖον (angeion), meaning vessel (angio- is almost always used to indicate a blood vessel. For example: an angiogram is an imaging study that looks at blood vessels.)
  • εκτείνειν (ekteinein), meaning extended (any time you see ectasia or ectasis, it means an abnormal dilation of a tubular structure. For example: bronchiectasis means dilation of bronchi.)

So telangiectasias are abnormal dilations of the very ends (tiny capillaries or venules) of blood vessels. They often occur in the skin and mucous membranes, and sometimes they look like tiny little spiders, but sometimes they just look like red blotches. Telangiectasias can also occur in the respiratory, gastrointestinal, and urinary tracts. Telangiectasias are not neoplastic (there aren’t any new, neoplastic vessels); they’re just malformations of existing vessels.

Hemorrhagic: Sometimes telangiectasias can rupture, causing nosebleeds, GI bleeding or hematuria.

That’s it! Now you know.

What’s the difference between an aortic dissection and a false aneurysm?

Q. I’m a little confused about the difference between an aortic dissection and a false aneurysm.

In diagrams of aortic dissection, it looks like all three layers of the vessel have been damaged and blood is leaking out of the vessel BUT still contained by connective tissue etc. Isn’t that what a false aneurysm is? So what’s the difference between the two?

A. I can see what you mean – diagrams of aortic dissections can be misleading!

Diagrams of aortic dissection (like this one above, from Wikipedia) often focus on the three types of dissections. The point of these diagrams is just to show the place in the aorta where the dissection begins (near the heart vs. more distally). They can be kind of misleading, though, if they don’t clearly depict how the blood tunnels through the wall of the aorta. Like you described, it can look more like the aorta has actually ruptured all the way through, and the blood is collecting outside the aorta.

So let’s quickly review the definitions of false aneurysm and dissection.

In a false aneurysm, all three walls of the vessel have been broken through, and blood collects just outside the vessel. It doesn’t tunnel down or up into the wall of the vessel at all. After some time, the blood organizes and becomes firm – kind of like a blood clot – and it prevents further blood from escaping the damaged vessel. 

In a dissection, only the inner portion of the vessel wall is damaged. Blood enters into that damaged area, and tunnels up or down within the wall of the vessel. Unlike a false aneurysm, in which blood bursts through all three layers of the vessel, in a dissection, the outer layers of the vessel are still intact, and blood forms a channel within the vessel wall itself.

So you had the right idea! It was just the diagram that threw you off. In the diagram above, the arrangement of the two little white arrows incorrectly implies that blood is busting all the way through the aorta at a single point – but the rest of the aortic wall looks intact. To really show what’s happening in an aortic dissection, the wall of the aorta should be more clearly depicted, and the second arrow should point up or down within the wall itself, showing the path of blood as forms a tunnel within the vessel wall. 


Dying of a broken heart


Valentine’s day can be a happy, candy-and-flowers day – but it can also be a day of loneliness and melancholy. Today’s post, written by our medical student correspondent Richard Huang, addresses the darker side of this Day of the Heart.  (more…)