Arachnodactyly or achromachia, is a condition in which the fingers are abnormally long and slender in comparison to the palm of the hand. It can be present at birth or develop in later life.

It is also seen in some cases that all or a few fingers can be bent backwards of 180 degrees.

Causes

This feature can occur on its own, with no underlying health problems. However, it can also be associated with certain medical conditions. Examples include Marfan syndrome

Marfan syndrome

Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers....

, Ehlers Danlos Syndrome and homocystinuria

Homocystinuria

Homocystinuria, also known as cystathionine beta synthase deficiency or CBS deficiency, is an inherited disorder of the metabolism of the amino acid methionine, often involving cystathionine beta synthase...

.

Arachnodactyly has been linked to mutations in both fibrillin-1

Fibrillin

Fibrillin is a glycoprotein, which is essential for the formation of elastic fibers found in connective tissue.Fibrillin is secreted into the extracellular matrix by fibroblasts and becomes incorporated into the insoluble microfibrils, which appear to provide a scaffoldfor deposition of elastin.It...

 and fibrillin-2

Fibrillin

Fibrillin is a glycoprotein, which is essential for the formation of elastic fibers found in connective tissue.Fibrillin is secreted into the extracellular matrix by fibroblasts and becomes incorporated into the insoluble microfibrils, which appear to provide a scaffoldfor deposition of elastin.It...

genes.