Progressive muscular atrophy

**Definition:** In progressive muscular atrophy, lower motor neuron signs in limb and trunk muscles are present without upper motor neuron involvement. Over time, some patients may progress to develop upper motor neuron signs, of which pathological evidence is common even in patients who never displayed clinical upper motor neuron signs, suggesting that progressive muscular atrophy is a form of ALS.

**Exclusions:** - Fazio-Londe syndrome - Amyotrophic lateral sclerosis