The Role of Cardiac MRI in the Evaluation and Management of Erdheim-Chester Disease: A Case Report (QF_TH_013)

Erdheim-Chester Disease (ECD) is a rare, non-Langerhans cell histiocytosis characterized by multisystem infiltration by abnormal histiocytes.¹ The disease predominantly affects males, accounting for 70-75% of cases. Cardiac involvement is common, occurring in 40-75% of cases, and has a significant impact on prognosis.^2–4 We present a case of a patient with ECD, who demonstrated cardiac involvement as assessed by cardiac magnetic resonance imaging (CMR).

A 48-year-old female presented with palpitations and exophthalmos and was diagnosed with ECD following biopsy from retro-orbital region. She was referred for CMR to evaluate potential cardiac involvement ahead of targeted therapy. Initial CMR demonstrated a diffuse thickening of the right atrioventricular groove involving the lateral right atrial wall and the interatrial septum. The lesion enfolded the aortic root, descending aorta and the roof of the left atrium. The findings were consistent with cardiovascular ECD.  Genetic test disclosed BRAF-V600E mutation, an activating mutation of the proto-oncogene BRAF often associated with ECD.⁵ The patient was treated with biological therapies targeting MAP-Kinase pathway⁶ (Cobimetinib and Vemurafenib), recently approved for histiocytic neoplasms. A follow-up CMR was performed to assess treatment response 4 months after initial scan.

Diagnostic Techniques and Their Most Important Findings:

The baseline CMR was performed using a 1.5T MR system. The CMR protocol included cine imaging in short-axis and trans-axial orientations across ventricles and atria, 3D whole-heart imaging as well as T1- and T2-weighted images and parametric T1/T2 maps. First-pass perfusion and late gadolinium enhanced (LGE) imaging was also carried out. The major findings were diffuse thickening of the lateral right atrial wall and right atrio-ventricular groove encasing the right coronary artery. With respect to myocardial signal intensity, the lesion was isointense on HASTE and b-SSFP images, and heterogeneously hyperintense on T2w images (Figure 1, C and D). Dynamic first-pass perfusion images revealed that the right atrial lesion was poorly perfused while heterogeneous LGE was seen on late post-contrast images (Figure 1, E and F). On follow-up scan, there was an interval reduction in mass size by approximately 30% compared to the baseline scan, suggesting a positive response to treatment.

Learning Points from this Case:

This case highlights the crucial role of CMR in the detection, assessment, and management of cardiac involvement in ECD. Specific CMR findings include diffuse thickening of the right atrial and atrio-ventricular groove with wrapping of the coronary arteries and aorta.⁴ CMR units are uniquely placed to increase awareness and improve the diagnostic yields of this rare disease, potentially playing a key role in monitoring the response to novel biological therapies.