Familial Congenital Facial Synkinesis Due to 12q Duplication: A Case Report and Literature Review.

Inverse Marcus Gunn phenomenon is a rare form of congenital facial synkinesis in which jaw movement temporarily elicits ptosis, either unilateral or bilateral. This phenomenon is presumed to result from dysinnervation of facial muscles during development of the nervous system. We describe 2 brothers, both with inverse Marcus Gunn phenomenon in the context of multiple other congenital anomalies, all presumed secondary to a chromosomal abnormality involving 12q duplication and 1p36 deletion. Although a handful of familial cases of congenital facial synkinesis have been previously described, this is the first in which a genetic abnormality has been identified. Of the 4 genetic abnormalities previously described in association with congenital facial synkinesis (based on isolated case reports), 1 also involved duplication at the long arm of chromosome 12. We conclude that duplication of ≥1 of the roughly 44 protein-coding genes in the ∼6.3-Mb overlap region between the previously published case and our 2 patients is a likely genetic cause of congenital facial synkinesis.