Our own Mutter Museum inspired science writer Carl Zimmer to meet and write about people who suffer from a rare and scary illness that causes extra bone growth. How rare? Zimmer explains on his blog:

They were born with a single mutation to a single gene that caused them to grow a second skeleton. Their condition, called fibrodysplasia ossificans progressiva, affects only one person out of every two million. If you traveled across the entire the United States and gathered everyone with the condition, you could fit them all comfortably on a single Greyhound bus.

I was inspired to meet them on a visit to Philadelphia last summer. The Mutter Museum, housed at the College of Physicians and Surgeons, is a collection of medical specimens of the sort you will see nowhere else in the United States. You feel an alternation of fear and exaltation at all the ways that the human body can be transformed. In one corner of the museum was the skeleton of a man named Harry Eastlack, who asked that his body be donated to science so that his disorder might someday be understood.

Looking at his skeleton, I wondered how on Earth something like this could happen, and what on Earth it was like to experience something like this.[The Atlantic, via The Loom]