What problems can come from chickenpox?

Usually nothing. : Chicken pox, the great majority of the time, will not cause any long term issues except for the possibility of scarring on the skin. However, a serious but rare complication from chicken pox is a chicken pox pneumonia. This usually requires hospitalization and can be fatal. Chicken pox with coughing or shortness of breath needs to be evaluated by a physician.

Rare but worrisome: In the pre-vaccine era we had 50 deaths, 10000 hospitilizations and in excess of 2 million cases/yr. Those infected have a 50X increase in risk of invasive strep bacteria through the skin sores. Chickenpox can produce a terrible pneumonia in newborns and adults, but most will have a mild disease. Later in life, the germ can return from hibernation in your body and cause shingles.