These eggs are perfectly fine to eat, and they will have the exact same properties as any other eggs. There can be several reasons for this to happen – either the chicken is old, or too young, and their egg laying systems are not functioning properly. It is also possible when the chicken is given antibiotics and hormones to promote more active egg laying. Finally, this can be due to excessive confinement, and as a result of a random mutation. The probabilities of getting these eggs is estimated to be 1 out of 1000. Just FYI – I am not an egg guru – it just happened to me once as well, and I did some research on the topic.