Erdheim-Chester disease (ECD) is a rare L-group histiocytosis. Orbital involvement is found in a third of cases, but few data are available concerning the radiological features of ECD-related orbital disease (ECD-ROD). Our aim was to characterize the initial radiological phenotype and outcome of patients with ECD-ROD.
Initial and follow-up orbital MRI from the patients with histologically proven ECD at a national reference center were reviewed. Pathological orbital findings were recorded for 45(33%) of the 137 patients included, with bilateral involvement in 38/45(84%) cases. The mean age of these patients was 60 years (+/- SD 11.3) and 78% were men. Intraconal fat infiltration around the optic nerve sheath adjacent to the eye globe (52%), with intense gadolinium uptake and fibrous component was the most frequent phenotype described. Optic nerve signal abnormalities were observed in 47% of cases. Two patients presented bilateral homogeneous extraocular muscle enlargement suggestive of a myositis-like involvement of ECD-ROD. None had isolated dacryoadenitis but in 17 eyes dacryodenitis was described in association with other types of orbital lesions. Only seven patients (15%) had normal brain MRI findings. ECD-associated paranasal sinus involvement and post-pituitary involvement were detected in 56% and 53% of patients respectively. A decrease/disappearance of the lesions was observed in 17/24 (71%) of the patients undergoing late (>12 months) follow-ups. Interestingly, ECD-ROD only rarely (7/45 (16%)) revealed the disease, with exophthalmos being the most frequently identified feature in this subgroup (3/45 (6%)). Even though ECD-ROD can be clinically silent, it constitutes a broad array of lesions often resulting in optic nerve signal abnormalities, the functional outcome of which remains to be established. ECD-ROD should thus be assessed initially and subsequently monitored by orbital MRI and ophthalmological follow-up.
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