Unilateral Transverse Arm Defect with Subterminal Digital Nubbins

We present a case of unilateral terminal transverse forearm deficiency with subterminal digit-like nubbins, identified in a fetus from a pregnancy terminated electively in the second trimester because the distal right arm and hand could not be seen by ultrasound and were presumed to be absent. Pathologic evaluation showed distal transverse shortening, tapering to a point in the mid-forearm. Five primitive digital nubbins were present, located just proximal to the tapered point. The arm vessels appeared normal histologically, and the amnion showed no evidence of intrauterine disruption. Histologic examination of the nubbins revealed osteocartilaginous tissue, never described previously within digital nubbins. This fetus has the rare phenotype of terminal transverse limb defects with residual nubbins, but differs in that the nubbins are not at the tip of the terminal transverse limb defect.