Misshapen eggs from chickens can be caused by a variety of diseases, conditions, and environmental factors. Here are some of the most common causes of misshapen eggs: Infectious bronchitis: This is a viral respiratory disease that affects chickens and can cause misshapen eggs, as well as reduced egg production and fertility. Egg drop syndrome: This is a viral disease that can cause soft-shelled, misshapen, or shell-less eggs. This disease can also cause a decrease in egg production. While the virus is naturally occurring in waterfowl such as ducks and geese, EDS occasionally finds its way into domestic chickens Avian influenza: