Long first metacarpal in monozygotic twins with probable Baller-Gerold syndrome.

We report on a pair of monozygotic twins with probable Baller-Gerold syndrome (BGS). Twin A had severe coronal craniosynostosis. Twin B had right radioulnar and ipsilateral first metacarpal hypoplasia. Both had bilateral fifth finger clinodactyly. Assuming that the twins were truly monozygotic, a single genetic disorder (i.e., BGS) could explain the variable expression. Together the twins have the typical anomalies of BGS. The diagnosis was supported by the metacarpophalangeal profile (MPP) which confirmed hypoplasia of the first right metacarpal in Twin A and bilateral fifth finger brachymesophalangy in both twins. Furthermore, the MPP showed an unexpected abnormal lengthening of the first metacarpal (unilateral in Twin A and bilateral in Twin B), a previously undetected radial ray defect in BGS. These findings suggest the possibility that the MPP may assist recognition of mild cases of BGS such as those with apparently isolated craniosynostosis or isolated upper limbs defects.