[Etiology and genetic aspects of Möbius sequence]

Möbius sequence is a rare congenital disorder defined by partial or complete agenesis of the 6th and 7th cranial nerves, which control eye movement and facial expression. The etiology is unclear but genetic and teratogenic factors are thought to be involved. Ischemia affecting the cranial nerve nuclei is a possible pathomechanism of Möbius sequence. Most cases of Möbius sequence are sporadic but some familial cases are also known. The inheritance patterns of Möbius sequence are heterogeneous and can be autosomal recessive, autosomal dominant or even X-linked. Some candidate regions and candidate genes have been described but no causative gene has yet been confirmed.