Synostosis affecting the RADIUS and ULNA characterized by limited forearm pronation and supination; limited elbow extension in Type 2. Radiologic examination shows proximal, smooth radioulnar fusion with absent radial head in Type 1 or radioulnar fusion distal to the proximal radial epiphysis with congenital radial head dislocation (Type 2). Inheritance may be autosomal dominant. it also is a feature of certain chromosome abnormalities, such as triple X-Y syndrome (XXXY). OMIM: 179300
