Progressive muscular atrophy
In PMA there is gradual loss of the lower motor neurons, so the muscles become steadily weaker and more wasted, causing weakness in the area they serve. This results in progressive muscle weakness, fasciculations (rippling effect under the skin), and shrinkage in muscle bulk and weight loss.
PMA occurs sporadically in the majority of affected individuals. Sporadic is the term used for cases of the disease where there is no family history.
PMA is related to ALS and, especially in the first 4 years after diagnosis, clinical evidence of upper motor involvement may become apparent in some people, leading to an ALS diagnosis. In other PMA patients, the physical effects may remain those of fairly pure lower motor neuron damage. Life expectancy, although variable, averages 5 – 10 years. Up to now, there is no cure or treatment for PMA, which is why there is much research devoted on PMA and the related motor neuron diseases ALS and PLS.