Syndactyly type 3 (SD3) is a limb abnormality present at birth that is characterized by complete fusion of the 4th and 5th fingers on both hands. In most cases only the soft tissue is fused, but in some cases the bones of the fingers (distal phalanges) are fused. SD3 is the characteristic digital abnormality in this condition. SD3 is inherited in an autosomal dominant manner.