A client with asthma has been taking prednisone daily for two years and is now in the emergency department complaining of back pain. An MRI of the spine shows a compression fracture of a vertebra. Which adverse effect of prednisone is most likely associated with these findings?

The correct answer is B: Osteoporosis. Prednisone is a corticosteroid known to cause bone loss and increase the risk of osteoporosis with long-term use. The mechanism involves suppression of osteoblast activity and promotion of osteoclast activity, leading to decreased bone density. This can result in vertebral compression fractures, as seen in the client's MRI. Fluid retention (A) is a common side effect of prednisone but is not directly related to vertebral fractures. Adrenal insufficiency (C) can occur with prolonged corticosteroid use, but it typically presents with symptoms such as fatigue and hypotension, not back pain. Gastrointestinal bleeding (D) is associated with NSAIDs, not corticosteroids.