June 5, 2007

Ripped from the headlines... Pathology Tuesday!

As I was listening to my podcasts from BBC World News and Anderson Cooper yesterday, I came across the skeleton of a male around 16-18 years old when he died. His wisdom teeth had erupted but weren't in full occlusion, and his long bones were not fully fused yet, indicating he still had some growing to do. As I laid out the bones, I noticed a small hole in the proximal end of the right radius, near the elbow joint. I figured this was probably taphonomic. When I got to the legs, there was a little ditch - not quite a hole - in the left tibia near the knee, but this one also looked taphonomic in nature. The last things I lay out before analyzing a skeleton are the small hand and foot bones. Imagine my surprise when, from of the bag of hands, I pulled this out:



Even though this bone is severely destroyed, it is the left fifth metacarpal (click here for what the bone should look like), which makes up the outside of your hand just under your pinkie finger. Often, the cause of roundish lesions in bone with destruction of the marrow cavity is osteomyelitis, a more or less generic term for the introduction of pyogenic (pus-producing) bacteria into a bone. Osteomyelitis is most often caused by either Staphylococcus or Streptococcus bacteria. However, osteomyelitis tends to confine itself to one bone (such as the radius) or an area of bone (such as the elbow joint). With this young adult male, I had involvement of the right elbow, the left knee, and the left metacarpal. After ruling out brucellosis (because of lack of spinal involvement) and echinococcosis (because of the multiple lesions), I think this individual suffered from tuberculosis.

As you probably all know from watching the news this week, Mycobacterium tuberculosis can be directly transmitted between humans through contact, usually through infected sputum coughed or sneezed up from the lungs, where the organism lives. Most people who are infected with tuberculosis are asymptomatic, and about one in ten infections leads to an active disease. If untreated, about half of people with the active disease die from tuberculosis. If an infected person is untreated or his body fails to fight the disease, it can spread through the bloodstream to the skeleton - particularly into areas rich in hematopoeic (red) marrow. Children and adolescents have more red marrow than adults because their bones are still growing; this means that tuberculosis can affect a wide variety of bones in growing subadults.

What I think happened in this metacarpal is that the mycobacteria moved to the diaphysis (shaft) of the bone and caused the blood supply to the bone to be cut off (ischemic necrosis). The cortex of the bone then began to resorb rapidly, resulting in the moth-eaten appearance. The head of the radius (near the elbow) and the top of the tibia (near the knee) are also common places for tuberculosis to appear in bone, although these sites are not nearly as destroyed as the metacarpal in this individual. Those areas were probably sites of infection that hadn't yet progressed to the necrotic stage.

It's still possible that this individual had a few osteomyelitic lesions rather than tuberculosis. However, it's rare for osteomyelitis to affect the metacarpals - unless you get bitten by someone (as, for instance, by punching them in the mouth) carrying strep or staph.

6 comments:

Lara said...

Wow, that's some wicked cool bone involvement. Ouch! It looks painful! I'm still waiting for you to find a skeleton with tertiary syphilis :) Found any trepanations yet?

Sara said...

Wow, KK, you know a lot of crap. I'm pretty sure I don't know as much CS as you know about bones and languages and stuff. Makes me wonder why you weren't any better at Trivial Pursuit. (Do you remember that question about the outfits the Germans wore in WWII?)

Kristina said...

Jeez, you can't tell the difference between natty uniforms and the SS, and suddenly you're a Trivial Pursuit pariah.

American Nationalist said...

I thought TB was a New World disease...

Kristina said...

New World disease? Heck no. There's evidence of Egyptian mummies having TB.

Sharon said...

Hi,

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If you need more information please email me back with the subject line as your URL.

Thank You,
Sharon Vegoe
Disease.com

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