| Brachydactyly type D | |
|---|---|
| Other names | Clubbed thumb,[1] thumb head,[2] short thumb,[3][1] potter's thumb,[1] royal thumb, murderer's thumb,[1] hammer thumb, stubbed thumb, stub thumb[4][5] |
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| Unilateral brachydactyly type D in an adolescent female | |
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| X-ray of a regular thumb (left) and a thumb with brachydactyly type D (right) showing distal phalangebrachyphalangy of said thumb. | |
| Specialty | Medical genetics |
Brachydactyly type D, also known asmurderer's thumb,[3][1]stubbed thumb,[4][5]spoon thumb, power thumb orshort thumb,[4][5] is a genetic trait recognised by athumb being relatively short and round with an accompanying widernail bed. Thedistal phalanx of such thumbs is approximately two-thirds the length of full-length thumbs. It is the most common type ofshortness of digits (brachydactyly), affecting approximately 2% of the population. It is associated with theHOXD13 gene, located onchromosome 2q31.1.[6]
Brachydactyly type D is a skeletal condition that exhibits a “partial fusion or premature closing of theepiphysis with thedistal phalanx of the thumb,” according to Goodmanet alia (1965).[5] J.K. Breitenbecher (1923) found that the distal phalanges of short thumbs were one-half the length of full-length thumbs, while R.M. Stecher (1957) claimed that it is approximately two-thirds. The condition may be unilateral (affecting one thumb) or bilateral (affecting both).[5]
Brachydactyly type D is agenetic trait. It exhibitsautosomal dominance and is commonly developed or inherited independently of other hereditary traits. The condition is associated with theHOXD13 gene, which is central indigital formation and growth.[4]
Various other studies supported an autosomal dominant pattern with reducedpenetrance.[7]
About 3% of Israeli Arabs had one or two short thumbs, compared with 1.6% amongAshkenazi as well as non-AshkenaziJews.[5] However, as the survey's Arab test persons were mainly recruited from a handful of large andclosely related clans living in a particular village, said percentage should be "considered with some reservation".
Cases of short thumbs have also been found in Eastern Nepal inJirel ethnic individuals from their participation in various epidemiologic studies. Some studies included taking radiographs of hands and wrists to examine their skeletal structure. Of the studied sample (which included 2,130 participants; 1,161 female and 969 male), 3.58% were found to have brachydactyly type D.[8]
The condition is also called clubbed thumb or club thumb.[9][10] American researcher R.A. Hefner used the terms "short thumb" and "brachymegalodactylism" in 1924,[3] and "short thumb" has continued to be used in a few other studies since then, including the study that definedRubinstein–Taybi syndrome in 1963.[1] "Stub thumb" is the common term preferred by the online databaseOnline Mendelian Inheritance in Man[4] and was first used in a 1965 study.[5] Stub thumbs have also been called murderer's thumb (allegedly amongfortune tellers),[5] hammer thumb, bohemian thumb, and potter's thumb.[4]
Well known individuals with this condition includeMegan Fox,James Doohan, Tyler Joseph,Buster Keaton,Dianne Buswell,Cillian Sheridan,Leighton Meester,Jinnytty,Miles Teller,Sanaa Lathan, Angelica Rose Due Galang, and Kasia fromIfeye.