Challenge of the Week / Hand & Wrist / 06.19.20

A defect in the apical ectodermal ridge (AER) will lead to which of the following types of congenital limb difference?
    • Transverse deficiency
    • The AER regulates proximal-to-distal limb development. Therefore, a defect in the AER results in a transverse deficiency.


    • Syndactyly
    • Syndactyly occurs as a result of failure of apoptosis in the developing web space.


    • Constriction band syndrome
    • Constriction band syndrome results from an amniotic band wrapping around an appendage in utero. This is a deformation rather than a malformation.


    • Mirror Hand
    • Mirror hand occurs as a result of a duplicated zone of polarizing activity (ZPA) such that both sides of the hand are ulnarized.



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