clinical features

Last reviewed 01/2018

Symbrachydactyly has a range of clinical presentation. At its most mild form, all digits are present but they are shorter than normal. The most common digit to be affected is the middle finger in which the middle phalanx is usually somewhat truncated. Typically, function is very good.

As the deficit worsens, progressively more bones are hypoplastic or absent along the line of the third ray with only a residual soft tissue 'nubbins' replacing the digit. The tendons to this ray may merge. With increasing severity, further rays have loss of phalanges - usually middle phalanx before distal phalanx - and metacarpals. There is a tendency for the deficiency to be on the ulnar side of the hand with sparing of the thumb.

Classically, the part of the symbrachydactyly spectrum with preservation of thumb and little finger but with rudimentary digital nubbins on the intervening digits was termed atypical cleft hand. However, in terms of its U-shaped cleft, sporadic nature and unilateral distribution it is clearly a different entity to classical cleft hand.

At its most extreme, there may be loss of the distal forearm with rudimentary nubbins on the end of the stump. The presence of rudimentary digits may be the only means of distinguishing symbrachydactyly from a transverse failure of formation.