Late-onset monomelic amyotrophy in a Caucasian woman.

We describe a 53-year-old Caucasian woman with a 19-year history of an evolving amyotrophy confined to her dominant right arm and hand. Although this atypical case of a late-onset monomelic amyotrophy in some respects mimics Hirayama disease or O'Sullivan-McLeod syndrome, it does not conform precisely with either of those disorders. We compare this individual's difficulties and clinical temporal profile to other disorders considered in the differential diagnoses with regard to her evolving clinical setting.