Thumb polydactyly with symphalangism.

Area of Science:

• Orthopedics
• Medical Genetics
• Developmental Biology

Background:

• Thumb polydactyly is a common congenital hand anomaly.
• Symphalangism, the fusion of digital rays, is a rare skeletal abnormality.
• The co-occurrence of these two anomalies in the thumb is exceptionally rare.

Purpose of the Study:

• To report three novel cases of thumb polydactyly associated with symphalangism.
• To discuss the potential molecular mechanisms underlying this rare combined anomaly.
• To evaluate the existing classification systems for thumb polydactyly in light of these findings.

Main Methods:

• Case series reporting clinical and radiographic findings.
• Literature review to identify similar cases.
• Discussion of potential pathogenetic mechanisms.

Main Results:

• Three patients presented with thumb polydactyly and symphalangism affecting specific digital components.
• Only one previously reported case of this specific combination was found in the literature.
• The anomaly's rarity is attributed to the simultaneous occurrence of distinct molecular events on different limb growth axes.

Conclusions:

• This combined anomaly represents a rare developmental defect of the hand.
• The etiology likely involves multiple, independent molecular events during limb development.
• Current classification systems for thumb polydactyly do not adequately encompass this presentation.