Arachnodactyly: Definition, Causes, Symptoms, Diagnosis and Treatment

It is a condition in which the fingers are long, thin, and sometimes curved.

This anomaly gets its name due to the similarity of the fingers to the long legs of a spider.

Dolichostenomelia, which refers to a longthin body, not just fingers, spider fingers, and achromatic, are some of the alternative names for arachnodactyly.

The formation of long, thin fingers may not be associated with any medical problems and may be expected.

However, “spider fingers” are often signs of an underlying disorder in some cases.

Causes of arachnodactyly

Arachnodactyly is associated with several genetic disorders that affect connective tissues in the body.

Connective tissues provide structure to the body and play an essential role in growth and development.


Examples of connective tissues include bones, skin, blood, and muscles.

Since connective tissues are involved in the growth process, genetic disorders that impact connective tissues can lead to abnormal growth.

In the case of arachnodactyly, certain genetic disorders increase the growth and development of the bones in the fingers and toes, causing them to become very long and thin.

Common genetic disorders associated with arachnodactyly include:

Marfan syndrome

This disorder causes the body to make faulty versions of the protein fibrillin-1, which forms connective tissues.

The production of defective fibrillin-1 proteins can cause abnormal growth and lengthening of bones throughout the body, including bones in the fingers and toes.


Homocystinuria is a genetic disorder that leads to the accumulation of homocysteine, an amino acid, in the body.

Homocysteine accumulation ​​can lead to connective tissue disorders, developing very long and thin fingers and toes.

Ehlers-Danlos syndrome

Ehlers-Danlos syndrome is another genetic disorder that affects collagen within connective tissues throughout the body.

Collagen is a protein used to give strength and structure to bones, skin, and other tissues.

Collagen is also essential for bone growth. Ehlers-Danlos syndrome causes the formation of weak and flexible collagen, which can result in the lengthening of the bones in the fingers and toes.

Also, arachnodactyly can occur in a person without any underlying health problems.

It should be noted that arachnodactyly itself, with long, thin fingers, does not cause any significant health problems.

However, genetic disorders that cause arachnodactyly can cause other abnormalities leading to significant health problems.

For example, Marfan syndrome can also result in an enlarged aorta that can lead to life-threatening heart problems.

The causes of arachnodactyly can include even other rare genetic disorders.

Although some children develop arachnodactyly at birth, the signs may become more apparent.

A doctor should be discussed if a baby has long, thin fingers and an underlying condition is suspected.


Among the most common symptoms are:

  • Marfan syndrome-like appearance (tall, thin person with an arm longer than the person’s height).
  • Long and slender fingers.
  • Ears »wrinkled. «
  • Prominent joint contractures from birth (especially knees, elbows, fingers, toes, and hips).
  • Long arched bones.
  • Muscle hypoplasia (underdeveloped muscles).

Arachnodactyly diagnosis

The doctor will perform a physical examination, where the medical history will be carried out, which includes questions such as:

  • When was it first noticed that the fingers had this shape?
  • Is there a family history of early death?
  • Does the patient have family members with known inherited disorders?
  • What are the symptoms present?
  • Have you noticed anything else unusual?

Most of the time, diagnostic tests are not necessary since the physical examination by itself is sufficient.

Treatment of arachnodactyly

Since arachnodactyly is often the result of a genetic disorder that a person is born with, there are no treatments that cure this condition.

Having long, thin fingers associated with arachnodactyly usually does not cause any severe health problems and, more often, does not require any treatment.

Sometimes the long fingers of arachnodactyly can make it difficult for a person to perform routine daily activities, such as writing.

A physical or occupational therapist can work with a person who has these difficulties.

A physical or occupational therapist can provide exercises and training to help a person with arachnodactyly cope with any problematic tasks in everyday life due to their long fingers.