Pneumonia may be caused by an infection or injury of the lungs.
Mammals breathe air with lungs.
Pneumonia may be caused by an infection or injury of the organs used to breathe air.
What may be caused by an infection or injury of the organs used to breathe air?

- Toxicity
- smoking
- fertilization
- pneumonia
- a broken leg
- oxygenation
- Dehydration
- the skin