Brachydactyly type D

Brachydactyly type D (BDD), also known as short thumb or stub thumb and inaccurately referred to as clubbed thumb, is a condition clinically recognized by a thumb being relatively short and round with an accompanying wider nail bed. The distal phalanx of affected thumbs is approximately two-thirds the length of full-length thumbs<ref>,

 Brachydactyly type D revisited, 
 American Journal of Medical Genetics Part A, 
 2010,
 Vol. 152A,
 pp. 2696–2701,
 DOI: 10.1002/ajmg.a.33632,</ref>. It is a type of brachydactyly, or shortness of digits, and is associated with the HOXD13 gene<ref>, 
 Homozygous nonsense mutation in the HOXD13 gene underlies synpolydactyly with incomplete penetrance, 
 European Journal of Human Genetics, 
 2004,
 Vol. 12,
 pp. 217–220,
 DOI: 10.1038/sj.ejhg.5201115,</ref>. Famous people with Brachydactyly type D include Megan Fox, Tyler Joseph, Leighton Meester, and Jonathan Lennox.

File:Brachydaktylie Typ D einseitig.jpg

Brachydaktylie Typ D einseitig

File:X-ray of a normal thumb next to a thumb with Brachydactyly type D.jpg

X-ray of a normal thumb next to a thumb with Brachydactyly type D

File:Clubbed thumb.jpg

Clubbed thumb

Signs and symptoms

Brachydactyly type D is characterized by a short and round thumb with a wider nail bed. The affected thumb's distal phalanx is approximately two-thirds the length of a typical thumb. The condition does not usually cause any functional limitations, and most individuals with BDD have normal hand function.

Genetics

Brachydactyly type D is associated with the HOXD13 gene, which is located on chromosome 2 and plays a crucial role in the development of limbs and digits during embryonic development<ref>,

 The HOXD cluster is a dynamic and resilient TAD boundary controlling the segregation of antagonistic regulatory landscapes, 
 Genes & Development, 
 2017,
 Vol. 31,
 pp. 2264–2281,
 DOI: 10.1101/gad.306769.117,</ref>. Mutations or alterations in the HOXD13 gene can result in a range of limb malformations, including BDD.

Diagnosis

Diagnosis of Brachydactyly type D is typically made through a physical examination and assessment of the thumb's appearance. In some cases, imaging studies, such as X-rays, may be used to confirm the diagnosis and determine the extent of the shortening of the distal phalanx. Genetic testing can be performed to identify alterations in the HOXD13 gene.

Management

Management of Brachydactyly type D primarily focuses on addressing any functional limitations or cosmetic concerns that an individual may have. In most cases, no specific treatment is required, as the condition does not typically cause functional limitations. However, if cosmetic concerns are significant or functional limitations are present, surgical interventions such as thumb lengthening or reconstruction may be considered<ref>,

 Surgical management of the thumb in patients with brachydactyly, 
 Techniques in Hand & Upper Extremity Surgery, 
 2009,
 Vol. 13,
 pp. 38–42,
 DOI: 10.1097/BTH.0b013e31819aaccb,</ref>.

Occupational therapy or physiotherapy may be beneficial for individuals who experience functional difficulties due to the shortened thumb. These therapies can help improve hand function and coordination, as well as address any pain or discomfort related to the condition.

Epidemiology

The exact prevalence of Brachydactyly type D is unknown, as the condition may be underdiagnosed due to its typically mild presentation. The condition has been reported in various populations around the world and does not appear to have a strong gender or ethnic predilection.

Notable cases

Several well-known individuals have been reported to have Brachydactyly type D, including:

• Megan Fox - American actress and model
• Tyler Joseph - American musician and member of the band Twenty One Pilots
• Leighton Meester - American actress, singer, and model
• Jonathan Lennox - Professional boxer

See also

• Brachydactyly
• HOXD13
• Thumb

External links

• Genetics Home Reference - Brachydactyly Type D
• National Organization for Rare Disorders - Brachydactyly Type D

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