Polysyndactyly
Polysyndactyly is a hereditary anatomical malformation combining polydactyly and syndactyly. There is also a type called crossed polysyndactyly.

Signs and symptoms
The way polysyndactyly presents itself varies; when the webbing is mild, it gives the appearance of the extra digit being partially connected to the (otherwise normal) digit next to it, when the webbing is extreme, the extra digit and the digit next to it will have the appearance of one rather enlarged digit (macrodactyly) and will have two or more finger/toe nails growing in the same digit (polyonychia). How the nails look will also vary, from separate supernumerary finger/toe nails to one very wide finger/toe nail.

References
External links
Polysyndactyly and Marfans syndrome The case of an Egyptian Jewish family with 17 affected members. The mother also had Marfans syndrome, which she passed on to a daughter who did not have polysyndactyly.