[2] All people with Holt-Oram syndrome have at least one abnormal wrist bone, which can often only be detected by X-ray.

[3] People with Holt–Oram syndrome may also have abnormalities in the electrical system that coordinates contractions of the heart chambers.

[1][2] People with Holt-Oram syndrome may have only congenital heart defects, only cardiac conduction disease, both or neither.

[1] The TBX5 gene produces a protein that is critical for the proper development of the heart and upper limbs before birth.

[2] If the symptoms aren't enough to diagnose, a person may undergo genetic testing for the mutations associated with the syndrome.