Ectrodactyly Or Split-Hand Syndrome

Ectrodactyly or split-hand syndrome/cleft hand syndrome, also known as Lobster-claw syndrome or Split hand/foot malformation (SHFM), came from the Greek word ektroma (abortion) and daktylos (finger). It is a rare inborn genetic disease where the hand is split on where the five fingers should be. Therefore creating a lobster claw-like hand.

According to the site, SHFM is caused by abnormalities at one of the multiple loci, including SHFM1 (SHFM1 at 7q21-q22), SHFM2 (Xq26), SHFM3 (FBXW4/DACTYLIN at 10q24), SHFM4 (TP63 at 3q27), and SHFM5 (DLX1 and DLX 2 at 2q31). SHFM3 is caused by submicroscopic tandem chromosomal duplications of FBXW4/DACTYLIN. SHFM3 is considered 'isolated' ectrodactyly and does not show a mutation in the tp63 gene.

Autosomal dominant with reduced penetrance is the most common mode of transmission, although autosomal recessive and X-linked forms rarely occur. Ectrodactyly is caused also by duplication of 10q24. The inheritance of cleft hand is autosomal dominant with a variable penetrance of 70%. Therefore, if the parent has
the condition, it is most likely the child will have it too.

There are many forms of Ectrodactyly. The most common form is Type I where a specific section in the human chromosome 7 contains two homeobox genes, DLX5 and DLX6.
Classification of Ectrodactyly:

Type
Description
Characteristics
I
Normal web
Thumb web space not narrowed
IIA
Mildly narrowed web
Thumb web space mildly narrowed
IIB
Severely narrowed web
Thumb web space severely narrowed
III
Syndactylized web
Thumb and index rays syndactylized, web space obliterated
IV
Merged web
Index ray suppressed, thumb web space is merged with the cleft
V
Absent web
Thumb elements suppressed, ulnar rays remain, thumb web space no longer present

The major symptoms of Ectrodactyly are lobster claw hands, an absence of the middle fingers, an absence of the middle toes, the presence of a single finger on the hand, and the presence of a single toe on foot. Cleft hands usually occur in the middle fingers and are V-shaped. However, it could occur in the thumb, and in rare cases, the little finger.

According to a site, the treatment of cleft hand is usually invasive and can differ each time because of the heterogeneity of the condition.
The function of a cleft hand is mostly not restricted, yet improving the function is one of the goals when the thumb or first webspace is absent. Children with ectrodactyly are not obligated to have surgery if the deformity is not too severe. However, if the child has cosmetic problems the doctor may advise having surgery when the child is 1-2 years old. People uses their hands for communication, but if one had different or deformity they could be rejected and ridiculed by society. When surgery is indicated, the choice of treatment is based on the classification. Techniques described by Ueba, Miura and Komada and the procedure of Snow-Littler are guidelines; since clinical and anatomical presentation within the types differs, the actual treatment is based on the individual
abnormality.
Treatment based on the classification of Manske and Halikis:

Type
Treatment
I/IIA
Reconstruction of the transverse metacarpal ligament
IIB/III
Transposition of the index metacarpal with reconstruction of the thumb webspace
IV
Mobility and/or position of the thumb of ulnar digit to promote pinch and grasp
V
There is no cleft or web space and the thumb is very deficient. This hand requires consideration of creating a radial digit

The goal of Snow-Littler is to make a wide first web space to minimise the cleft in the hand. The index digit will be transferred to the ulnar side of the cleft. Concurrently, a correction of index malrotation and divergence is performed. To minimise the cleft, it is necessary to fix together the metacarpals which used to border the cleft and through repositioning the flaps, the wound can be closed. In ueba, transverse flaps are used to resurface the palm, the rear side of the transposed digit and the ulnar part of the first web space. A tendon graft is used to connect the extensor tendons of the border digits of the cleft to prevent digital separation during extension. The closure is simpler but has a cosmetic disadvantage because of the switch between the palmar and rear skin. Miura and Komada is similar to the Snow-Littler, the only difference is the closure of the first webspace done by simple closure or Z-plasties.

To summarize it all, ectrodactyly is a rare inborn disease where one’s hands are cleft with the absence of the middle finger or the presence of a single finger on the hand forming a V-shape. SHFM3 is caused by submicroscopic tandem chromosomal duplications of FBXW4/DACTYLIN and is considered 'isolated' ectrodactyly and does not show a mutation in the tp63 gene. Ectrodactyly is caused also by duplication of 10q24. And the most common form of ectrodactyly is Type I. There are many types of treatment based on classification and techniques such as Snow-Littler, Ueba, and, Miura and Komada.