The cause of amniotic constriction band is uncertain. Some believe it is a developmental issue (a “dysplasia” resulting from abnormal development of the structures) and others believe that it is a “deformity” that results from banding or pressure on previously normal structures. Either way, at the time of birth, a variety of differences can be noted.
Banding, or ringing, of a finger, forearm, or leg can occur. This is usually a problem only with appearance but deeper bands can also affect function. Amputations (possibly from extremely tight bands or direct pressure in utero) can also occur. The amputations usually affect fingers (or toes) or parts of fingers (or toes). Finally, syndactyly (abnormal joining of the fingers) can also occur. This type of syndactyly differs from other forms as the fingertips are joined whereas there are fenestrations (or holes) between the fingers closer to the hand. Sometimes the tips of multiple fingers are joined together. It is common for more than one extremity to be affected.
In the pictures below, the thumb and small finger are normal. The index, long, and ring fingers are short due to amputations. The long and ring fingers are syndactylized (joined at tip) but there is a fenestration between the digits.
|Amniotic constriction band affecting short central fingers with a perforation (fenestration) between the fingers.|
|Palmar view of central digits affected by amniotic constriction band.|