A four-year-old boy from Watertown City, New York is developing extra skeleton because of a rare disease and will eventually become stiff for life.

Kimberley Hayes, a 4th-grade teacher at Watertown City School District's Knickerbocker Elementary School, revealed to Watertown Daily Times on Thursday that his son, Shane, has been diagnosed with fibrodysplasia ossificans progressiva (FOP), which affects only 600 people worldwide.

FOP is a genetic disorder that causes bone to form in muscles, tendons, ligaments and other connective tissue. FOP expert and researcher Dr. Frederick S. Kaplan of the University of Pennsylvania School of Medicine said people with the condition can live up to 41 years and would be locked in a standing or sitting position.

There is no treatment for the condition but Kaplan and his colleagues, who discovered the FOP gene in 2006, are looking for a cure.

Shane's mother was unaware of the condition until lately, when the boy figured in a sledding mishap that cause his shoulder to flare up and his stomach began puffing out. Doctors could not figure out the cause prompting Mrs. Hayes to take his son to the Children's Hospital Boston and learned Shane has FOP.

The mother has kept Shane mostly at home and is taking extra caution in caring for him to avoid injury to his son.