Second Face Syndrome is one of the rarest conditions ever diagnosed. In May 2010, the syndrome was brought to the public thanks to a brave 14 month old boy living with the condition in China. The condition causes a very wide mouth and cleft, in this case, that leaves the boy looking like he is wearing a mask at all times.
What looks like a mask is really the upper part of the face. As the upper and lower jaw does not meet, the boy is unable to close his mouth or chew thus resulting in severe malnutrition. After being told a large sum of money would be needed to correct the condition, parents were delighted to hear a hospital in Shanghai would be doing the required surgeries for free.
The medical term for second face syndrome is Macrostomia. Typically Macrostomia results in a wider than normal mouth. Aside from surgery to correct the defect, there is no known cure or cause of second face syndrome.