Abdominal involvement in Erdheim-Chester disease (ECD): MRI and CT imaging findings and their association with BRAF mutation.

Objectives: To use magnetic resonance imaging (MRI) and computed tomography (CT) to define abdominal involvement in Erdheim-Chester disease (ECD), and to investigate the association between these findings and the BRAF mutation.

Methods: This prospective study was performed on 61 ECD patients (46 men). The MRI and CT imaging studies were reviewed independently by two experienced radiologists. The association between BRAF mutation and imaging findings was analysed using Fisher's exact test, and odds ratios with 95% confidence intervals.

Results: Perinephric infiltration was the most common finding (67%), followed by involvement of proximal ureters (61%). In 56% of cases, infiltration extended to the renal sinuses, and in 38% caused hydronephrosis. Adrenal gland infiltration was present in 48% of patients. Infiltration of renal artery (49%) and aorta (43%) were the most common vascular findings, followed by sheathing of celiac, superior mesenteric artery (SMA) or inferior mesenteric artery (IMA) (23%). The BRAF mutation was positive in 53% of patients with interpretable BRAF sequencing. There was a statistically significant association between this mutation and perinephric infiltration (p = 0.003), renal sinus involvement (p < 0.001), infiltration of proximal ureters (p < 0.001), hydronephrosis (p < 0.001), adrenal gland involvement (p < 0.001), periaortic infiltration (p = 0.03), sheathing or stenosis of renal artery (p < 0.001) and sheathing of other aortic branches (p = 0.04).

Conclusions: Renal and vascular structures are the most commonly affected abdominal organs in ECD patients. Some of these findings have significant positive association with the BRAF mutation.

Key Points: • Abdominal imaging plays a crucial role in management of Erdheim-Chester disease. • Significant associations exist between BRAF mutation and several abdominal imaging findings. • Considering several associations, evaluating BRAF mutation status is recommended in ECD patients.