NOG-related symphalangism spectrum disorder
An autosomal dominant condition caused by pathogenic variants of the NOG gene, encoding the noggin protein. Five overlapping clinical syndromes associated with NOG mutations have been described; proximal symphalangism, multiple synostoses syndrome 1, tarsal-carpal coalition syndrome, stapes ankylosis with broad thumbs and toes, and brachydactyly type B2. NOG-related symphalangism spectrum disorder is a new term initially proposed by Potti et al., 2011 to encompass these disorders. NOG-SSD is characterized by proximal symphalangism, conductive deafness caused by stapes ankylosis, ocular abnormality such as hyperopia and strabismus, and characteristic facial features including a broad, tubular-shaped nose and a thin upper vermilion.