A Traumatic Traveler

FES is a rare complication associated with long bone fractures and orthopedic manipulation.^1,2 The exact mechanism of fat emboli production is unknown, but two theories prevail. The mechanical theory states that an outside mechanical source causes bone marrow contents or adipose tissue contents to be dislodged into the circulation where they travel through the venous circulation to become embedded in the lungs.^1,2 These fragments may also migrate to the arterial circulation, through a patent foramen ovale or intrapulmonary shunts, leading to end organ damage.^1,2 The biochemical theory suggests that fat emboli in the venous circulation precipitate an inflammatory and prothrombotic cascade that triggers fibrin production, platelet aggregation, and release of free fatty acids into the circulation, predisposing patients to develop multifocal systemic emboli.¹

Although the classic triad in FES includes respiratory symptoms, rash, and CNS symptoms, all three findings are only present in 1%-29% of cases.^1,2 Respiratory abnormalities, ranging from tachypnea and dyspnea to ARDS and hypoxic respiratory failure, occur in up to 75% of patients with FES.¹ Central nervous system (CNS) complications, including headache, confusion, coma, seizures, and death caused by cerebral ischemia, occur in up to 86% of patients.^1,2 Petechiae may occur in 20%-60% of patients and are usually located on nondependent regions of the body such as the head, neck, and chest.

Diagnosis of FES is largely clinical and requires a high index of suspicion and elimination of other conditions, including pulmonary thromboembolism, diffuse intravascular coagulation, and sepsis. The CNS complications must be differentiated from CNS infection, stroke, migraine, benign intracranial hypertension, and intracranial hemorrhage. There is no gold standard test for diagnosis. The Gurd and Wilson criteria, modified Gurd criteria, and Schonfeld’s criteria (Table) are commonly used but have not been clinically validated.^1,3-5 These use a combination of clinical signs of respiratory distress, neurological symptoms, petechial rash, and various other diagnostic factors. When patients have risk factors, such as trauma, surgery, or predisposing conditions (eg, mobility-limiting neuromuscular disorders) and signs and symptoms potentially consistent with FES, the diagnostic evaluation should include arterial blood gas analysis, complete blood count, chest radiographs, and coagulation studies. Ophthalmological exam to evaluate for cotton-wool spots, brain MRI to detect cerebral emboli, and CT pulmonary angiogram to assess for pulmonary infarcts may help to eliminate other diagnoses and/or confirm FES.

Diagnosis of uncommon conditions that present with nonspecific symptoms, like FES, can be challenging because the symptoms may overlap with many other possible diagnoses. This challenge is further exacerbated in patients with significant medical complexity, as with the patient discussed here. Specifically, this patient had multiple plausible explanations for CNS symptoms and respiratory symptoms. It was ultimately the visual symptoms that began to link his symptoms together into a unifying syndrome and the ophthalmologic examination that prompted confirmatory imaging. It is important to continually revisit and revise the differential diagnosis in patients with medical complexity and avoid the competing temptations to abandon the search for a unifying diagnosis and attribute all symptoms to a patient’s underlying condition.

Treatment of FES is largely supportive with close monitoring of neurological status and providing supplemental oxygen as needed. Corticosteroids have been suggested to help prevent FES in patients with long bone fractures, but there is no evidence to suggest they are helpful once FES is diagnosed.² There is conflicting evidence for the efficacy of heparin or low-molecular-weight heparin as treatment in FES.^2,6 After discussions with consulting physician teams, the patient, and his family, enoxaparin and aspirin were started for this patient in light of his tenuous condition in order to decrease the risk of further embolic complications.

Patients with DMD and other neuromuscular disorders likely have a greater propensity to develop FES even after minor trauma.^1,6 This is believed to be caused by patients becoming nonambulatory early in life and receiving substantial corticosteroid therapy, which can lead to osteopenia and fatty replacement of the bone marrow.^1,6 This population is also often obese by the second or third decade of life, which contributes to their already increased propensity to fall.^1,6

To our knowledge, this patient is 1 of 18 reported cases of FES after trauma in DMD patients. Two-thirds of these cases occurred when an unrestrained patient fell from their wheelchair. The other cases occurred while walking, during physical therapy, and during assisted transfers.^6-12 In these cases, FES had a guarded prognosis, with 7 of the 18 patients dying and 1 of the patients remaining in a persistent vegetative state.^8,9 While caution is warranted in generalizing these findings, given the small number of reported cases and likely publication bias,education of caregivers and patients on use of restraints and safe transfers is paramount to limit the risk of trauma.

Primary caregivers, especially those who care for people with chronic medical conditions, often report that their opinion is undervalued.¹³ In this case, the patient’s mother correctly ascertained the diagnosis of FES upon the patient’s initial presentation, although this diagnosis was sidelined by the healthcare professionals in favor of the presumptive diagnosis of aspiration pneumonia. It was several days after the patient’s mother postulated this diagnosis, and only after many diagnostic considerations were excluded, that the diagnosis of FES rose to the top of the medical team’s differential diagnosis. It can be challenging to diagnose and manage illness in patients with chronic, complex medical problems, and the strong advocacy of their caregivers may be met with clinician defensiveness. However, patients with chronic complex medical conditions, along with their parents and/or caregivers, are often rich sources of knowledge and expertise about those conditions—making them key members of the diagnostic team. Intentionally involving parents and caregivers in the decision-making process (eg, through family centered rounds that begin by focusing on addressing parental concerns) is known to reduce medical errors and improve outcomes.¹⁴