Ectrodactyly
Encyclopedia
Ectrodactyly, sometimes referred to as the “Lobster-Claw Syndrome” involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly are often described as "claw-like" and may include only the thumb and one finger (usually either the little finger, ring finger, or a syndactyly
of the two) with similar abnormalities of the feet.
, craniofacial manifestations, hernias, hearing loss, and mental retardation. Translocations in 7q do not have as many abnormalities but are generally associated with most hearing loss cases. This is why most cases of ectrodactyly are generally accompanied by another abnormality or linked to another syndrome (ex. EEC, LMS, ECP). Detailed studies of a number of mouse models for ectrodactyly have also revealed that a failure to maintain median apical ectodermal ridge (AER) signalling can be the main pathogenic mechanism in triggering this abnormality.
A number of factors make the identification of the genetic defects underlying human ectrodactyly a complicated process: the limited number of families linked to each split hand/foot malformation (SHFM) locus, the large number of morphogens involved in limb development, the complex interactions between these morphogens, the involvement of modifier genes, and the presumed involvement of multiple gene or long-range regulatory elements in some cases of ectrodactyly. In the clinical setting these genetic characteristics can become problematic and making predictions of carrier status and severity of the disease impossible to predict.
In 2011, a novel mutation in DLX5
was found to be involved in SHFM.
Those with ectrodactyly are contributing members of society with their own jobs and careers; many choose to have families and raise children. In most daily tasks the health condition appears to have a small effect on their functionality. In 2006, the London Tate
exhibition Single Shot featured a video of an unidentified person with ectrodactyly skillfully playing the piano with only four fingers.
According to M.P. Ferreira, a case of ectrodactyly was found in a two month old male mixed Terrier
dog. In another study, Carrig and co-workers also reported a series of 14 dogs with this abnormality proving that although ectrodactyly is an uncommon occurrence for dogs, it is not entirely unheard of.
Syndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...
of the two) with similar abnormalities of the feet.
Genetics
A large number of human gene defects can cause ectrodactyly. The most common mode of inheritance is autosomal dominant with reduced penetrance, while autosomal recessive and X-linked forms occur more rarely. Ectrodactyly can also be caused by deletions, translocations, and inversions in chromosome 7 (7q). The deletions in 7q can result in a contiguous gene syndrome that includes growth impairment, microcephalyMicrocephaly
Microcephaly is a neurodevelopmental disorder in which the circumference of the head is more than two standard deviations smaller than average for the person's age and sex. Microcephaly may be congenital or it may develop in the first few years of life...
, craniofacial manifestations, hernias, hearing loss, and mental retardation. Translocations in 7q do not have as many abnormalities but are generally associated with most hearing loss cases. This is why most cases of ectrodactyly are generally accompanied by another abnormality or linked to another syndrome (ex. EEC, LMS, ECP). Detailed studies of a number of mouse models for ectrodactyly have also revealed that a failure to maintain median apical ectodermal ridge (AER) signalling can be the main pathogenic mechanism in triggering this abnormality.
A number of factors make the identification of the genetic defects underlying human ectrodactyly a complicated process: the limited number of families linked to each split hand/foot malformation (SHFM) locus, the large number of morphogens involved in limb development, the complex interactions between these morphogens, the involvement of modifier genes, and the presumed involvement of multiple gene or long-range regulatory elements in some cases of ectrodactyly. In the clinical setting these genetic characteristics can become problematic and making predictions of carrier status and severity of the disease impossible to predict.
In 2011, a novel mutation in DLX5
DLX5
Homeobox protein DLX-5 is a protein that in humans is encoded by the DLX5 gene.- Function :This gene encodes a member of a homeobox transcription factor gene family similar to the Drosophila distal-less gene. The encoded protein may play a role in bone development and fracture healing...
was found to be involved in SHFM.
Hearing loss
As mentioned in the Genetics section, ectrodactyly can be caused by various changes to 7q. When 7q is altered by a deletion or a translocation ectrodactyly can sometimes be associated with hearing loss. Ectrodactyly, or Split hand/split foot malformation (SHFM) type 1 is the only form of split hand/ malformation associated with sensorineural hearing loss.Functionality
The functional utility of the malformed limbs is discussed in issue 2481 of The British Medical Journal. The affected persons can perform work that requires skillful manipulation, regardless of their handicap. The article says, “The needlework of some of the females is good; the handwriting of most is excellent. One individual is a boot maker, two others drive cabs, none finding difficulty in clothing themselves, and most do so with extraordinary rapidity, even to the lacing of boots....It is said of one that he is able in this way to lift pins from the floor with his feet.”Those with ectrodactyly are contributing members of society with their own jobs and careers; many choose to have families and raise children. In most daily tasks the health condition appears to have a small effect on their functionality. In 2006, the London Tate
Tate
-Places:*Tate, Georgia, a town in the United States*Tate County, Mississippi, a county in the United States*Táté, the Hungarian name for Totoi village, Sântimbru Commune, Alba County, Romania*Tate, Filipino word for States...
exhibition Single Shot featured a video of an unidentified person with ectrodactyly skillfully playing the piano with only four fingers.
Ectrodactyly in species other than humans
Ectrodactyly is not only a genetic characteristic in humans, but can also occur in frogs and toads, mice, salamanders, cows, chickens, rabbits, marmosets, cats and dogs, and even West Indian manatees. The following examples are studies showing the natural occurrence of ectrodactyly in animals, without the disease being reproduced and tested in a laboratory. In all three examples we see how rare the actual occurrence of ectrodactyly is.Wood Frog
The Department of Biological Sciences at the University of Alberta in Edmonton, Alberta performed a study to estimate deformity levels in Wood Frogs in areas of relatively low disturbance. After roughly 22,733 individuals were examined during field studies, it was found that only 49 Wood Frogs had the ectrodactyly deformity.Salamanders
In a study performed by the Department of Forestry and Natural Resources at Purdue University, approximately 2000 salamanders (687 adults and 1259 larvae) were captured from a large wetland complex and evaluated for malformations. Among the 687 adults, 54 (7.9%) were malformed. Of these 54 adults, 46 (85%) had missing (ectrodactyly), extra (polyphalangy) or dwarfed digits (brachydactyly). Among the 1259 larvae, 102 were malformed, with 94 (92%) of the malformations involving ectrodactyly, polyphalangy, and brachydactyly. Results showed few differences in the frequency of malformations among life-history changes, suggesting that malformed larvae do not suffer substantially higher mortality than their adult conspecifics.Cats and dogs
In a “Journal of Heredity” published by the Oxford Journals a study was performed to test allele frequencies in domestic cats. Among the 265 cats observed, there were 101 males and 164 females. Only one cat was recorded to have the ectrodactyly abnormality, illustrating this rare and unique disease.According to M.P. Ferreira, a case of ectrodactyly was found in a two month old male mixed Terrier
Terrier
A terrier is a dog of any one of many breeds or landraces of terrier type, which are typically small, wiry, very active and fearless dogs. Terrier breeds vary greatly in size from just a couple of pounds to over 70 pounds and are usually categorized by size or function...
dog. In another study, Carrig and co-workers also reported a series of 14 dogs with this abnormality proving that although ectrodactyly is an uncommon occurrence for dogs, it is not entirely unheard of.
Human genetic disorders
Ectrodactyly is frequently seen with other congenital anomalies, or other birth defects. Syndromes in which ectrodactyly is associated with other abnormalities can occur when two or more genes are affected by a chromosomal rearrangement. Disorders associated with ectrodactyly include Ectrodactyly-Ectodermal Dysplasia-Clefting (EEC) syndrome, which is closely correlated to the ADULT syndrome and Limb-mammary (LMS) syndrome, Ectrodactyly-Cleft Palate (ECP) syndrome, Ectrodactyly-Ectodermal Dysplasia-Macular Dystrophy syndrome, Ectrodactyly-Fibular Aplasia/Hypoplasia (EFA) syndrome, and Ectrodactyly-Polydactyly. More than 50 syndromes and associations involving ectrodactyly are distinguished in the London Dysmorphology Database.Notable people
- Bree WalkerBree WalkerBree Walker is a radio talk show host, actress, and disability-rights activist, who gained fame as the first on-air American television network news anchor with ectrodactyly. Walker worked as a news anchor and/or reporter in San Diego, New York City, and Los Angeles.Walker was born in Oakland,...
Once a popular television anchor woman in Los Angeles, she has appeared in the television drama “Nip/TuckNip/TuckNip/Tuck is an American drama series created by Ryan Murphy, which aired on FX in the United States. The series focuses on McNamara/Troy, a plastic surgery practice, and follows its founders, Sean McNamara and Christian Troy...
” as an inspirational character who battles her disease and counsels another family who have children with ectrodactyly. - Grady Stiles Sr. and Grady Stiles Jr.Grady StilesGrady Franklin Stiles, Jr. was a freak show performer. His deformity was ectrodactyly, where the fingers and toes are fused together to form claw-like extremities. Stiles' stage name was the "Lobster Boy"....
- Vadoma Tribe in Africa
- Mikhail TalMikhail TalMikhail Tal was a Soviet–Latvian chess player, a Grandmaster, and the eighth World Chess Champion.Widely regarded as a creative genius, and the best attacking player of all time, he played a daring, combinatorial style. His play was known above all for improvisation and unpredictability....
, chess World Champion - Lord Lokhraed, guitarist and singer of french Black Metal band Nocturnal Depression, has ectrodactyly on his fretting hand
- Mohammed Abdellaoue, Norwegian footballer who plays in Hannover96