Bilateral asymmetry in cone epiphysis of the middle phalanx, fifth finger

The form of epiphyseal-diaphyseal dysostosis in the phalanges of the hand having the appearance of a cone-and-crater (cone-shaped epiphysis) is a common variant in otherwise normal individuals. Dysplasia on the radial margins of the epiphysis and diaphysis, typically resulting in clinodactyly, is another variant and is also common in Down's syndrome. Both variants frequently involve brachymesophalangia. The strong female bias in cone epiphyses and the lack of such bias in dysplasia not involving cones has led to the interpretation of distinct etiologies for the two patterns. A single case displaying brachymesophalangia with cone epiphysis in the middle phalanx of the left fifth finger and brachymesophalangia with clinodactyly in the corresponding bone of the right hand is reported. This is evidence that in certain cases the two patterns of mid-5 dysostosis are manifestations of the same condition.