Progressive Muscular Atrophy - Disease or Syndrome?

Disease or Syndrome?

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 neurones the most important lesion, whereas in ALS it was the upper motor neurone degeneration that was primary, with lower motor neurone 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 neurone 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.

Also, no gene has been linked specifically to PMA, and the disorder does not appear in the OMIM database.

In favour of considering PMA a separate disease, some patients with PMA live for decades after diagnosis, which would be unusual in typical ALS.

To this day, terminology around these diseases remains confusing because in the United Kingdom motor neurone disease refers to both ALS specifically and to the spectrum of ALS, PMA, PLS, and PBP. In the United States the most common terms are ALS (both specifically for ALS and as a blanket term) or Lou Gehrig's disease.