A 19-year-old man is admitted to the hospital for surgical management of a closed, comminuted femoral shaft fracture sustained in a motor vehicle accident 24 hours ago. While awaiting surgery, the patient suddenly develops acute shortness of breath and confusion. On physical examination, his temperature is 37.0°C (98.6°F), pulse is 115/min, and blood pressure is 110/70 mmHg. Pulse oximetry shows an oxygen saturation of 88% on room air. Neurological exam reveals disorientation to time and place but otherwise no focal deficits. Examination of the skin reveals several non-blanching, reddish-brown macules over the base of the neck and bilateral axillae.
Which of the following is the most likely finding on funduscopic examination?
The correct answer is:
C) Intraretinal hemorrhages and intravascular fat globules
This patient presents with the classic triad of fat embolism syndrome (FES): hypoxemia, neurological abnormalities, and a petechial rash. FES most commonly occurs 12–72 hours following the fracture of a long bone, such as the femur. While the diagnosis is primarily clinical, ocular findings, including Purtscher-like retinopathy, can occur when fat emboli enter the microvasculature of the eye. This manifests as cotton wool spots, intraretinal hemorrhages, and occasionally the visualization of fat globules within the retinal arterioles.
Answer choice A: Cherry-red spot at the macula, is incorrect. This is the classic finding of a central retinal artery occlusion (CRAO) or certain lysosomal storage diseases (e.g., Tay-Sachs). While fat emboli can cause ischemia, the diffuse Purtscher-like pattern is more characteristic than an isolated cherry-red spot.
Answer choice B: Diffuse retinal whitening and edema, is incorrect. While localized whitening (cotton wool spots) occurs, diffuse whitening of the entire retina is more typical of a CRAO rather than the embolic shower seen in FES.
Answer choice D: Optic disc edema with blurred margins, is incorrect. This describes papilledema, which is caused by increased intracranial pressure. While FES causes neurological symptoms due to cerebral microemboli, it does not typically present with the generalized increased ICP required to cause papilledema unless there is a massive stroke or cerebral edema.
Answer choice E: Pale, opaque retina with a "boxcarring" appearance of the vessels, is incorrect. This describes the late stages of a aentral retinal artery occlusion where blood flow has slowed significantly.
Key Learning Point
Fat embolism syndrome is a clinical diagnosis following long-bone or pelvic fractures characterized by the triad of respiratory insufficiency, neurological impairment, and a petechial rash. Ocular manifestations, though not part of the primary triad, include intraretinal hemorrhages and cotton wool spots caused by microvascular fat emboli. Treatment is primarily supportive, including high-flow oxygen and, in severe cases, mechanical ventilation.
