Progressive muscular atrophy

Progressive muscular atrophy (PMA), also called Duchenne–Aran disease and Duchenne–Aran muscular atrophy, is a disorder characterized by the degeneration of lower motor neurons, resulting in generalized, progressive loss of muscle function.

PMA is classified among motor neuron diseases (MND) and it sporadically appears during adulthood. It is speculated that about 2.5%-11% of adult onset MND is PMA, making it less common than ALS.

PMA affects only the lower motor neurons, in contrast to amyotrophic lateral sclerosis (ALS), the most common MND, which affects both the upper and lower motor neurons, or primary lateral sclerosis, another MND, which affects only the upper motor neurons.

The history of PMA involved determining if it was a separate disease from ALS or if it was just the earlier stages of ALS. In the end, scientists considered PMA its own disease that was under the same category as ALS. The signs and symptoms of PMA are similar to ALS but are located in a different region of the body, but the diagnosis can be more complex due to the nature of PMA and ALS. The prognosis of PMA can be longer than ALS because it affects less of the motor neurons. The options for treatment are small and are still being explored, from the theory of stem cell treatment to simple physical therapy. Although there is no cure, there some possible treatments such as; physical therapy and some medications that can slow progression.

Despite being rarer than ALS, PMA was described earlier, when in 1850 French neurologist François Aran described 11 cases which he termed atrophie musculaire progressive. Contemporary neurologist Guillaume-Benjamin-Amand Duchenne de Boulogne English: /duːˈʃɛn/ also claimed to have described the condition 1 year earlier, although the written report was never found. The condition has been called progressive muscular atrophy (PMA), spinal muscular atrophy (SMA), Aran–Duchenne disease, Duchenne–Aran disease, Aran–Duchenne muscular atrophy, and Duchenne–Aran muscular atrophy. The name "spinal muscular atrophy" is ambiguous as it refers to any of various spinal muscular atrophies, including the autosomal recessive spinal muscular atrophy caused by a genetic defect in the SMN1 gene.

Since its initial description in 1850, there has been debate in the scientific literature over whether PMA is a distinct disease with its own characteristics, or if lies somewhere on a spectrum with ALS, PLS, and PBP. Jean-Martin Charcot, who first described ALS in 1870, felt that PMA was a separate condition, with degeneration of the lower motor neurons the most important lesion, whereas in ALS it was the upper motor neuron degeneration that was primary, with lower motor neuron degeneration being secondary. Such views still exist in archaic terms for PMA such as "Primary progressive spinal muscular atrophy". Throughout the course of the late 19th century, other conditions were discovered which had previously been thought to be PMA, such as pseudo-hypertrophic paralysis, hereditary muscular atrophy, progressive myopathy, progressive muscular dystrophy, peripheral neuritis, and syringomyelia.

The neurologists Joseph Jules Dejerine and William Richard Gowers were among those who felt that PMA was part of a spectrum of motor neuron disease which included ALS, PMA, and PBP, in part because it was almost impossible to distinguish the conditions at autopsy. Other researchers have suggested that PMA is just ALS in an earlier stage of progression, because although the upper motor neurons appear unaffected on clinical examination there are in fact detectable pathological signs of upper motor neuron damage on autopsy.

As a result of lower motor neuron degeneration, the symptoms of PMA include: