nemaline myopathy

ACEM

Interpretation of the EM image

The electron microscopist must be aware of the normal structure of the tissue under examination, and also, more importantly, must be aware of the range in normal appearance.
Skeletal muscle undergoes a variety of ultrastructural changes in response to disease. However, it is nearly always the case that the changes are not specific to any one disease or condition.

Skeletal muscle is made up of bundles of fibres (called fascicles) which are in turn bound together by connective tissue. Under the electron microscope individual fibres can be closely examined. Fibres consist of fibrils which are regularly aligned along the length of each muscle fibre. Fibrils are made up of fine filaments which have a maximum diameter of 20nm.

Ultrastructural changes in nemaline myopathy

Nemaline comes from the Greek word nema meaning “threadlike”, which was one of the descriptions given to the structures when first seen at the light microscope level.

In the low magnification image the fibrillar structure is disorganised and the thin dark bands (Z lines) are thickened. The thickened Z lines have formed nemaline rods, which, at higher magnification, can be seen to be a lattice like structure.

Nemaline rods can be seen from time to time in a number of conditions, and in both degenerating and regenerating muscle fibres, but when there is a clinical suspicion of nemaline myopathy, and no other significant pathological process is evident in the muscle (other than the presence of many nemaline rods) then the diagnosis of nemaline myopathy can be made. click to enlarge image:-

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