What is arachnodactyly?
It is the spider-like fingers of patients with Marfan’s. Described in 1896 by the homonymous Frenchman in a
5-year-old patient, the term arachnodactyly was actually coined 6 years later by Achard. The fingers are
thin and long, resembling “the bent legs of a spider.”
To test for it, use the Marfan’s thumb sign: ask patients to open their hands and cross their thumbs over their palms as far as possible; then ask them to fold the fingers across the thumb and make a fist. The test is positive if any part of the thumb sticks out beyond the ulnar surface of the fist. The sign is typical of
Marfan’s, but also can occur in other conditions of joints’ hypermobility, like Ehlers-Danlos.
It is the spider-like fingers of patients with Marfan’s. Described in 1896 by the homonymous Frenchman in a
5-year-old patient, the term arachnodactyly was actually coined 6 years later by Achard. The fingers are
thin and long, resembling “the bent legs of a spider.”
To test for it, use the Marfan’s thumb sign: ask patients to open their hands and cross their thumbs over their palms as far as possible; then ask them to fold the fingers across the thumb and make a fist. The test is positive if any part of the thumb sticks out beyond the ulnar surface of the fist. The sign is typical of
Marfan’s, but also can occur in other conditions of joints’ hypermobility, like Ehlers-Danlos.