Orbital MRI Pre- and Post-Vemurafenib Therapy for Erdheim-Chester Disease.

Abstract

Figure 1A shows an axial T1 postcontrast MRI of the orbits from a patient with Erdheim–Chester disease prior to treatment with BRAF inhibitor, vemurafenib. Bilaterally, there is near complete replacement of the retrobulbar fat with isointense, mildy enhancing masses. The rectus muscles are thinned and there is osseous remodeling as evidenced by bowing of the lamina paprycea. At this time, the patient’s vision was 20/200 OD, 20/20 OS with a right relative afferent pupillary defect. There was near complete ophthalmoplegia OU, and his exophthalmometry readings were 28 mm OD, 26 mm OS. Figure 1B shows a comparable axial T1 post contrast MRI of the orbits 10 weeks after beginning vemurafenib. During this time, the patient was on a prednisone taper from 60 mg daily to a nadir of 25 mg daily at the time of last follow up. There is marked reduction in the size of the retrobulbar masses, left greater than right. Clinically, the patient’s vision improved to 20/40 OD with resolution of the relative afferent pupillary defect and remained 20/20 OS. His motility normalized with the exception of a slight adduction deficit OD. Follow-up exophthalmometry was 15 mm OU. The etiology of Erdheim–Chester disease is unknown, and as such, traditional treatments have been suboptimal. The recent identification of a proinflammatory oncogene-induced senescence mechanism associated with a BRAFV600E mutation has opened the door for targeted therapy with vemurafenib in some patients. Vemurafenib works by inhibiting the B-Raf/MEK step on the B-Raf/MEK/ERK pathway.FIG. 1: Axial T1 post contrast MRI pre- (A) and post- (B) Vemurafenib therapy for Erdheim-Chester disease.