대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Erdheim-Chester Disease

Radiologic Findings

Fig 1. Chest PA shows the massive amount of left pleural effusion and total collapse of Lt. lung. Also Rt. Pleural effusion is seen in the right hemithorax.
Fig 2. Chest CT also reveals massive left pleural effusion and moderate right pleural effusion without pleural nodularities or thickening.
Fig 3-5. During 1 month, bilateral pleural effusion was drained and Lt. pleurodesis was done. Mild pleural thickening and pericardial thickening is newly developed. Interstitial thickening and mild patchy GGOs is seen in both lungs. The whole bony thorax has sclerotic changes.

Brief Review

Brief Discussion
Erdheim-Chester Disease (ECD) is a rare form of non-Langerhans cell histiocytosis characterized by multisystem involvement. Although children may occasionally also be affected, its occurrence peaks in middle-aged adults with 5th-7th decades. There is a slight male predominance.
Since 2012, it is discovered in a large proportion of ECD patients that mutations in the MAPK pathway in over 80% of patients have been identified, at least half of them being the BRAFV600E activating mutation.
Clinical manifestations of ECD vary among individuals, ranging from an indolent focal disease to a life threatening organ failure. Also ECD symptoms vary depending on the site of involvement and are nonspecific.
The diagnosis of ECD is often a challenge, and requires integration of descriptive pathology with clinical and radiographic findings.
Lung involvement in ECD is seen radiologically in 30��50% of cases, involving either the lung parenchyma or pleura. The most frequent finding on CT is an interstitial lung disease-like pattern with smooth interlobular septal thickening. Other findings on CT of the chest may include mediastinal infiltration, pleural thickening or effusions, ground-glass opacities, or centrilobular opacities.
Also cardiovascular involvement can be seen in 50% to 70% patients. Most common finding is pericardial or myocardial infiltration with effusion. Circumferential soft tissue sheathing of the thoracic/abdominal aorta and its branches may be seen as ��coated�� aorta.
The skeletal involvement is most commonly seen. Bilateral symmetric osteosclerosis at the metadiaphysis of lower extremity bones (femur, tibia, and fibula) is seen in 95% cases and is pathognomonic. Skull and axial skeleton less commonly involved than LCH, which typically shows lytic punched-out lesions rather than sclerotic lesions that are seen in ECD
Differential diagnosis includes Langerhans cell histiocytosis and immunoglobulin G4 (IgG4)-related disease.
The traditional treatment is based on immunomodulatory agents (interferon-��). Since the detection of MAPK pathway activation in most patients and the dramatic efficacy of BRAF and MEK inhibitors, these targeted treatments represent the first-line approach in patients with severe disease forms including life-threatening cardiac or neurologic involvement.
18F-FDG PET-CT is considered the best modality for ECD response assessment and should be performed 3-6 months after initiation of therapy. CT or MRI of specific systems affected, such as the heart, brain, or orbit, could be obtained 3-6 months after diagnosis and every 6-12 months if the disease stabilizes. Treated lesions may not fully regress; however, this may not reflect the disease's activity.

In this case, the patient was diagnosed with Erdheim-Chester disease through excisional biopsy of the pleura, and BRAF mutation was negative. The patient died from respiratory failure before starting treatment.

References

1. Goyal, Gaurav, et al. "Erdheim-Chester disease: consensus recommendations for evaluation, diagnosis, and treatment in the molecular era." Blood, The Journal of the American Society of Hematology 135.22 (2020): 1929-1945.
2. Pegoraro, Francesco, et al. "Erdheim

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