Pathological findings in sporadic inclusion body myositis and GNE myopathy

The following study compared the pathological findings between sporadic inclusion body myositis (sIBM) and Glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase myopathy (GNEM) patients.

An enzyme histochemistry was used to compare the pathological characteristics between 11 patients with sIBM and 16 patients with GNEM.

There were four pathological differences observed: (1) A majority of the rimmed vacuoles found in the sIBM patients resembled cracks, whereas the GNEM patients (P=0.004) had round or oval vacuoles. (2) A majority of the rimmed vacuoles that were located in the periphery of the atrophic muscle fibers of the sIBM patients. The patients with GNEM had a majority of the rimmed vacuoles in the center of the atrophic muscle fibers (P=0.001). (3) The patients with sIBM had basophilic granules in the rimmed vacuoles, which appeared to be fine granules that were sand-like particles. The GNEM patients had coarse granules (P=0.018). (4) The proportion of mononuclear cells invasion of muscle fibers was larger in the sIBM patients than the GNEM patients (P=0.047). The GNEM patients were younger on average than the sIBM patients at the onset of symptoms (P<0.001) and at the diagnosis age (P<0.001). The electromyography (EMG) showed the presence of myogenic lesions in 10 patients with sIBM, both myogenic and neurogenic lesions in one patients with sIBM and myogenic lesions in 16 patients with GNEM.

There were significant differences in the morphologies of the rimmed vacuoles between sIBM patients and GNEM patients.