After photos of Star Trek star Leonard Nimoy in a wheelchair with an oxygen mask surfaced on the web, the actor took to Twitter to explain that he has chronic obstructive pulmonary disease (COPD). Spock wrote: "I quit smoking 30 yrs ago. Not soon enough. I have COPD. Grandpa says, quit now!!" He continued to address the topic of smoking, saying, "Smokers, please understand. If you quit after you're diagnosed with lung damage it's too late. Grandpa says learn my lesson. Quit now." COPD is an umbrella term that covers lung diseases like emphysema, chronic bronchitis, asthma, and bronchiectasis.