This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fracture Neck of Femur, Subject name: Orthopaedics
A 30 year old man had a road traffic accident and sustained fracture of femur. Two days later he developed sudden breathlessness. The most probable cause can be: 
Select and explain. 
A. Pneumonia, B. Congestive heart failure, C. Bronchial asthma, D. Fat Embolism
D: Fat Embolism
Answer: D: Fat Embolism 
Explanation: Ans. D. Fat EmbolismThe fat globules released from the bone marrow (due to trauma/orthopedic procedures) are deposited in the pulmonary capillary bed. This causes ischemia and inflammation. The symptoms appear 12-72 hours after the trauma. Initial symptoms are tachycardia and tachypnea. There may be high spiking fever and non-palpable petechiae, especially over upper body.Neurological symptoms like agitation, delirium, stupor and coma can occur. (The fat globules may cross the pulmonary circulation via arteriovenous connections).