Congenital unilateral orbital fibrosis with suspected prenatal orbital penetration.

Congenital fibrosis of the extraocular muscles includes various abnormalities ranging from isolated fibrosis of a single muscle to bilateral involvement of all extraocular muscles. Congenital unilateral orbital fibrosis is a specific fibrosis syndrome with only five cases previously reported. Although these reports postulated that a prenatal orbital inflammatory process caused the fibrosis, no etiology was proposed, nor was a mechanism suggested for entrance of the inflammation into the orbit. We discuss three additional cases in which evidence suggested prenatal orbital penetration. In one, a dense scar was found at birth from the skin of the upper lid to beyond the trochlea. The second had a dense fibrous tract extending from the upper lid skin to the trochlea and beyond into the orbit without a skin scar. These lesions could have been inflicted by the fetuses' own fingers or toes or, in the second case, by the twin fetus. The third had a benign mesenchymoma of the nasopharynx and skull that had eroded the medial orbital wall, which was seen on computed tomography scan but not on routine x-rays. The nature of the inflammatory substance is unknown. There was no other evidence of inflammation or infection in the eight reported cases. Possibly amniotic fluid itself, entering the orbit "late" in gestation, might cause this inflammation. We recommend that all children with congenital unilateral orbital fibrosis be examined specifically for defects in the orbit, and that computed tomography be employed rather than plain x-rays.