Description: Ectrodactyly, or split hand or split foot malformation is a birth defect that involves the absence of some fingers or toes, and the fingers or toes beside the missing fingers are fused together. It is a rare limb malformation. The term “ectro-“ means loss or absence, while the term “dactyl” refers to a digit like a toe or finger. The missing fingers or toes that combined with clefts gives a webbing appearance which leads to the condition called “lobster claw syndrome”. It normally has minimal effect on the life of people with the condition. Ectrodactyly exists in two different forms, either as a single disorder or as part of a syndrome. It is normally inherited from either parent as an autosomal dominant form. Ectrodactyly can be caused by various genetic factors. The most common type of ectrodactyly is caused by mutation of chromosome 7 which contains DLX5 and DLX6 genes. Autosomal recessive and X-linked forms are less frequent to happen. Common abnormalities associated with ectrodactyly include craniofacial defects, tibial aplasia, and genitourinary abnormalities. Ectrodactyly-ectodermal dysplasia-clefting syndrome (EEC) is the one example of ectrodactyly accompanied by several organ defects. Other syndromes such as Goltz syndrome, Carpenter’s syndrome, Miller syndrome, and DeLange syndrome also associated with ectrodactyly.
Causes/History: Ambroise Paré was the first reference to the idea of a cleft hand in 1575. The first report of true cleft hand was written by Hartsink in year 1770. Ectrodactyly was first discovered by the Stiles family in 1805. William Stiles was the first person in Stiles family that was diagnosed with symptoms of Ectrodactyly. After that, the Stiles family passed down the disease to their future generations. Grady Franklin Stiles Jr. was the sixth generation in a line that had inherited the mutated genes. The first operation of cleft hand was performed in 1896 by Doctor Charles N. Dowed of New York City.The main treatment for Ectrodactyly is surgery. Surgery is necessary for those patients which have deformity is too severe and they are not able to use the hands for any activity. The surgery is performed very early in the life of the child if the deformity is severe. The purpose of the surgery is to close the cleft so that they can use their hands to hold things and correct other deformity that are present.
Case study: Ectrodactyly occurs 1 in 90,000 births therefore it is a rare disease. This genetic disorder does not occur in any particular area. According to statistics, both males and females have the equal possibility to inherit this genetic factor. A variety of human gene defects may cause ectrodactyly. The most common type of inheritance is autosomal dominant form that is usually inherited from either parent that carries the gene. It is usually caused by mutation of chromosome 7, more specifically a translocation or deletion of a specific part on this chromosome. There are also cases of ectrodactyly that are inherited as an autosomal recessive form and X-linked but they occur more rarely. Ectrodactyly can also be caused by a duplication on chromosome 10. The anomaly of ectrodactyly causes development of secondary to the chromosomal mutations which results in failure of Apical Epidermal Ridge(AER) to produce molecules that stimulate nearby cells to differentiate into digital rays. The failure in maintaining a normal apical ectodermal ridge that can ensure full development of the limb leads to failure to differentiate the autopod. In ectrodactyly, the hand or foot appears to be splitting into two halves due to the failure to develop the phalanx, metatarsal and metacarpal bones of one or more digits. However, there is no big effect on the person with the disease. They still carry on with their normal lives and have regular life expectancy.
A six-year-old boy presented with malformation in hands and feet since he was born. There were median clefts of two hands. There was syndactyly of the ring finger with middle finger and that of the thumb with the index finger in his left hand and, there was syndactyly of the index finger and thumb in the right hand. The X-rays showed normal metacarpals in both hands but absence of terminal phalanges of the middle finger in both hands. Both the feet also had a deep median cleft. There was syndactyly with absence of several metatarsals in both feet. There was no other difference in body structure. Physical examination was normal. The child was a smart student and had proper development for his age. He was a child of non-consanguineous marriage and the delivery was a natural vaginal delivery with no perinatal events. His first sibling was a female baby. The female baby also had similar deformed hands and feet. There is no any abnormal features besides this abnormality. There was no family history of this abnormality in both the parents or any of the relatives. This case is caused by the mutation in chromosome 7 which causes the HOX gene can not function well in development of the limb buds and T-box genes such as Tbx4 and Tbx5 did not function well in determining limb identity.