Commonest cause for bilateral proptosis in children is -
Most common cause of bilateral proptosis: In children : Neuroblastoma and leukemia (chloroma). In adults : Thyroid ophthalmopathy. Most common cause of unilateral proptosis: In children : Orbital cellulitis. In adults : Thyroid ophthalmopathy. Ref: A. K. Khurana 6thE pg404
Cavernous hamangioma
Chloroma
Fibrous histiocytoma
Rhabdomyosarcoma
Diseases of orbit, Lids and lacrimal apparatus