Mutations in the GARS gene cause Charcot-Marie-Tooth 2D and distal spinal 
muscular atrophy type V - allelic disorders characterized by predominantly 
distal upper extremity weakness and atrophy, typically beginning during the 
second decade of life. We report monozygotic twin girls with onset of weakness 
in infancy and a previously reported GARS mutation within the anticodon-binding 
domain. The severity and remarkable similarity in phenotypes of these girls and 
the reported case suggest that mutations within the anticodon-binding domain are 
more damaging to aminoacyl tRNA synthetase function than those within other 
domains of GARS.