Brachydactyly () is a medical term denoting the presence of abnormally short digits (fingers or toes) at birth. The shortness is relative to the length of other long bones and other parts of the body. Brachydactyly is an inherited, dominant trait. It most often occurs as an isolated dysmelia, but can also occur with other anomalies as part of many congenital syndromes. Brachydactyly may also be a signal that one is at risk for congenital heart disease due to the association between congenital heart disease and Carpenter syndrome and the link between Carpenter syndrome and brachydactyly.
Nomograms for normal values of finger length as a ratio to other body measurements have been published. In clinical genetics, the most commonly used index of digit length is the dimensionless ratio of the length of the third (middle) finger to the hand length. Both are expressed in the same units (centimeters, for example) and are measured in an open hand from the fingertip to the principal creases where the finger joins the palm and where the palm joins the wrist.
Causes
Generally, brachydactyly is inherited through an autosomal dominant trait (The exact gene may differ see "Types" table for specific genes). However exceptions could exist due to antiepileptic medicines taken during pregnancy or low blood flow to the extremities during infancy.
Symptoms
Symptoms of isolated brachydactyly include shorter bones in the hands and feet. This could include, phalanges, metacarpals, metatarsals, carpals, and tarsals. Different types of isolated brachydactyly have different symptoms and they are grouped according to what areas they affect.
Prognosis
Isolated brachydactyly does not affect the wellbeing nor longevity of one's life, in most cases treatment is not necessary. However, type A3 and type D are relatively common, affecting around 2% of the population. Particularly high prevalence of brachydactyly type D was reported among Israeli Arabs and in the Japanese population. Type A3 was found at an especially high frequency of 21% among Japanese schoolchildren.
Types
There are several types of brachydactyly:
{| class="wikitable"
! Type !! OMIM !! Gene !! Locus !! Also known as
|Description
|-
|Type A1, BDA1|| || IHH BDA1B || 5p13.3-p13.2, 2q33-q35 || Brachydactyly type A1 or Farabee-type brachydactyly.
|BDA1 is an autosomal dominant inherited disease. Features include: short or absent phalanges, extra carpal bones, hypoplastic or absent ulna and short metacarpal bones.
|-
|Type A2, BDA2|| || BMPR1B GDF5 ||20q11.2, 4q23-q24|| Brachydactyly type A2, Brachymesophalangy II or Brachydactyly Mohr-Wriedt type.
|Type A2 is a very rare form of brachydactyly. The phalanges of the index fingers and second toes are shortened.
|-
|Type A3, BDA3|| || HOXD13|| || Brachydactyly type A3, brachymesophalangy V or brachydactyly-clinodactyly.
|Type A3 only shortens the middle bone of the little finger.
|
|-
|Type B, BDB (or BDB1)|| || ROR2 || 9q22|| Brachydactyly type B or Cooks syndrome.
|Type B affects the final bones of all eight fingers. It causes the bone to be shortened or missing entirely. The same thing happens to the corresponding toes. The final thumb bones and big toe bones may be split or flatter than average.
|Most common form of brachydactyly. It shortens the final bone in the thumbs and does not affect the fingers at all.