[Benign, focal amyotrophy].

Benign focal amyotrophy is a usually asymmetrical motor neuron disease affecting young people. Its favourable prognosis differentiates it from progressive motor neuron diseases such as the much more frequent and most severe form, amyotrophic lateral sclerosis (ALS). We report on one patient with "juvenile muscular atrophy of unilateral upper extremity" of the Hirayama type and two patients with selective amyotrophy of one calf ("wasted leg-syndrome"). In addition, we have observed three young women with selective muscle atrophy in the scapula region which has appeared stable for many years and might represent another entity of so-called benign focal amyotrophy.