Skiagraphs (X-rays) of the hands and feet of a 12-year-old girl with ectrodactyly
Colloquially known as “lobster-claw syndrome”, ectrodactyly is the congenital absence or deficiency of one or more of the central digits of the hand or foot. It generally manifests bilaterally (on both sides), but not always with identical deformity on either side.
In addition to the loss or shortening of the central digits, “clefting” of the hand or foot often divides the carpals or tarsals down the middle-line, giving the extremity the claw-like appearance that is associated with the condition. While there are many genetic anomalies that can cause ectrodactyly, most of them are autosomal dominant, and parents with the condition have a 50/50 chance of passing it on to their children.
Aside from unusual appendages, a majority of people with ectrodactyly are not otherwise hindered by other mental or physical defects. A large percentage with the most common forms of ectrodactyly have hearing deficits, but normally not to a serious enough degree to require a hearing aid.
The Vadoma (or Doma) people of Zimbabwe, and the Kalanga tribes of Zimbabwe and Botswana, both have significantly higher rates of ectrodactyly than the rest of the world. With the Vadoma, their long-term isolation from other peoples resulted in an inbreeding-depression with an autosomal dominant form of tarsal ectrodactyly. The origin of the higher rate of the condition in the Kalanga is not known for certain, as it is a different mutation than in the Doma.
Röntgen Rays and Electro-Therapeutics. Mihran Krikor Kassabian, 1907.