For the differential diagnosis of adult-onset spinal muscular atrophy (SMA IV) it is important to remember, at least in males, the following disorders: X-linked spinal and bulbar muscular atrophy (SBMA, also known as Kennedy disease, caused by a CAG trinucleotide repeat expansion in the androgen receptor gene), nemaline myopathy, which can show late-onset in at least 4% of cases, central core disease and X-linked myotubular myopathy, Charcot-Marie-Tooth hereditary neuropathy, Guillain-Barré syndrome, adrenomyeloneuropathy (a phenotype with onset in the late twenties caused by ABCD1), Pompe disease (caused by GAA mutations), hexosaminidase A deficiency, distal spinal muscular atrophy and amyotrophic lateral sclerosis (ALS).
In females, disorders caused by mutations on the X-chromosome may not be considered with priority.
