Brachydactyly type A2 is a very rare condition affecting the middle bone (middle phalanx) of the index finger and the second toe. Typically, people affected by brachydactyly type A2 have very short (hypoplastic) middle bones of these digits. In some individuals, the bone above the middle phalanx (distal phalanx) is shifted as well, so that the fingers and toes may look misshapen. There have not been reports of other symptoms associated with brachydactyly type A2. Typically, brachydactyly type A2 does not require surgery, and affected individuals are able to use their hands normally.

BMPR1B or GDF5. Mutations in areas of the genetic code that control a gene called BMP2 can also cause brachydactyly type A2.

In families with multiple cases of brachydactyly type A2, it seems that the condition is inherited in an autosomal dominant manner. This means that every child of a person affected by the condition has a 50% chance of having the condition themselves.