Inclusion body myopathy associated with motor neuron syndrome: three case reports

Hereditary inclusion body myopathy (h-IBM) is an autosomal-recessive or autosomal-dominant hereditary disease characterized by peculiar findings in muscle biopsies which resemble those occurring in inclusion body myositis (IBM). The absence of an inflammatory infiltrate in myofibers in h-IBM is a relevant differential criterion between the two pathologies. Motor neuron diseases (MND) represent a group of disorders involving both upper and lower motor neurons, characterized by fasciculations, progressive muscle weakness, and muscle atrophy. The most common form and prototype of MND is the amyotrophic lateral sclerosis (ALS) or Charcot's Disease, a progressive and fatal neurodegenerative disorder occurring in late adulthood. The pathogenesis of ALS remains still unknown, a variety of hypotheses having been proposed to account for the disease. The association of both pathologies is not common and offers new hypotheses about the pathogenic mechanisms in skeletal muscle and nervous system degeneration.

Described are three case reports in which we observed the clinical, laboratory and histopathological association of IBM and MND. In one case, dementia was also present. Muscle data was obtained by muscle biopsies and immunohistochemistry, while diagnosis of MND was supported by common neurophysiological techniques.

The accumulation ofphosphorylated neurofilaments with a hereditary IBM-like pattern in skeletal muscle fibers without accumulation of amyloid-beta protein was observed.

A better knowledge of the mechanisms in cellular death cascade could explain the pathogenesis of these different degenerative disorders.