Isolated limb reduction defects occur in approximately 1 in 2000 live births within which central ray anomalies are an important subgroup. Most affected persons have mild or moderate functional impairment. Considerable psychological morbidity may also occur. While there have been major strides forwards in our understanding of vertebrate limb development, the mechanisms responsible for central ray deformities remain poorly understood. Several case reports of central clefting anomalies associated with chromosomal rearrangements or interstitial deletions of 7q21.2-q21.3 suggest that this chromosomal region is important for limb development.