[Erdheim-Chester disease presenting with bilateral orbital involvement: Report of three cases]

To report treatment outcomes of orbital tumors associated with Erdheim-Chester disease and to highlight the importance of systemic work-up in patients presenting with bilateral proptosis.

Three patients with Erdheim-Chester disease, whose initial manifestation was bilateral proptosis, were retrospectively studied. The course of onset, clinical, imaging and histopathological features, systemic associations and response to treatment were reviewed. The main outcome measures were Hertel measurements and orbital tumor regression on imaging studies.

All patients presented with bilateral non-pulsatile proptosis resistant to retropulsion and headeache without specific localization. Magnetic resonance imaging studies showed bilateral intraconal orbital tumors. Incisional biopsy of these tumors demonstrated CD68+, CD1a-, and S100- histiocytic infiltrates consistent with the diagnosis of Erdheim-Chester disease. The BRAFV600E mutation was found in all cases. Systemic work-up revealed asymptomatic bony involvement in the lower extremities, perirenal fibrosis, central nervous system and cardiac involvement. All patients initially received pegylated interferon-α2a, which resulted in excellent responses except for the orbital tumors. Two patients were then treated with vemurafenib, which resulted in rapid regression of the orbital lesions.

Pegylated interferon-α was highly effective in the control of cardiac, perirenal, skeletal and cerebral involvement but not the orbital tumors. The infiltrative orbital lesions of Erdheim-Chester disease would appear more responsive to vemurafenib.