When staining with hematoxylin and eosin of a muscle biopsy from a patient with T341P desminopathy, we observe accumulations of inclusions similar to nuclei (arrows in figures 1 and 2, x280). And outside of these accumulations - adipose tissue, which used to be muscle tissue. There are no such massive accumulations of inclusions in adjacent muscle fibers. We assume that clusters of inclusions are not nuclei? Figure 2 is the inverted figure 1.
Desminopathy, particularly the T341P variant, is a type of myopathy characterized by the accumulation of abnormal intermediate filaments composed of desmin in the cytoplasm of muscle cells. These inclusions are not typically found in nuclei and can instead be seen as aggregates within the cytoplasm. The presence of adipose tissue outside of the inclusions suggests that the affected muscle fibers have undergone degeneration or necrosis.
The observations you described in the muscle biopsy from a patient with T341P desminopathy are consistent with the pathological changes seen in this condition. Desminopathies are a group of rare inherited muscle diseases caused by mutations in the desmin gene, which encodes the desmin protein. The T341P mutation is known to cause desmin aggregation, leading to the formation of inclusions in muscle fibers. These inclusions are composed of aggregated desmin and other structural proteins, and they can interfere with the normal functioning of muscle fibers.
The accumulations of inclusions that you observed that resemble nuclei are consistent with desmin aggregates. The fact that they are not observed in adjacent muscle fibers suggests that the aggregates are selective and only affect certain areas of the muscle. The presence of adipose tissue, which used to be muscle tissue, is also consistent with the degeneration and loss of muscle fibers in this condition.
Have you confirmed they are indeed not nuclei? These look entirely consistent with inflammatory cell and/or scavenging macrophage infiltration, especially the way you can clearly see a degenerating myofibre with multiple inclusions in the centre: this is a hallmark of macrophage-mediated 'cleaning up' of damaged/necrotic tissue..
A really easy check for this would be to just stick on an intercalating nuclear dye (DAPI, Hoechst or similar) and see if those spots in the centre fluoresce brightly. If "yes", you could also try immunostaining with a macrophage marker, or a pan leukocyte marker, or both.
Dear Geir Bjorklund, Duc M. Hoang, John Hildyard, thank you very much for your answers and recommendations!
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