Arachnodactyly - Causes and Symptoms

Definition

Arachnodactyly is a skeletal deformity that determines tapered and disproportionately long fingers relative to the palm of the hand or the sole of the foot. These ends can also be unusually flexible, similar to the legs of a spider.

The arachnodactyly is recognized by the positivity of the "thumb sign", which consists in closing the fist with the thumb inside and noting the protrusion of the distal phalanx of the same finger, beyond the ulnar border. Another useful examination in the evaluation is the "sign of the wrist": the distal phalanges of the thumb and little finger overlap, if placed to encircle the wrist.

Arachnodactyly can be congenital and develop in the context of various genetic diseases. Other people may experience this pathological lengthening of fingers and toes over time, in infancy or adulthood.

Arachnodactyly is a symptom of Marfan syndrome and depends on an alteration in collagen metabolism. This deformity is also among the anomalies that can be found in homocysteine and in Beals syndrome (a connective tissue disease that occurs similarly to Marfan syndrome). In some cases, however, arachnodactyly can occur in the absence of an underlying disease.