“Necklace” fibers as a late clue to the interpretation of the forgotten “trilaminar” fibers

Excerpt

In a recent article by Bevilacqua et al. [1] on “necklace fibers, a new histological marker of late-onset MTM1-related centronuclear myopathy”, impressive light micrographs of such fibers are presented which closely resemble those previously described as “trilaminar” fibers [2‐4], as far as the different techniques applied at the earlier and present times allow identification. Both the clinical and the structural changes appear rather similar within a wide spectrum of individual variations. Ringel et al. [2] in 1978 reported on a sporadic myopathy with pronounced rigidity, lack of spontaneous movements, and increased CK values. Electromyography appeared to be normal. The muscle biopsy at the age of 7 weeks showed numerous fibers with three concentric zones leading to the designation as trilaminar fibers. The innermost zone showed accumulations of mitochondria, glycogen, and electron dense material with only few remnants of myofibrils. The intermediate zone consisted of myofibrils showing Z-band streaming. The outer zone resembled a sarcoplasmic mass. Histochemistry revealed extrajunctional acetylcholine receptor (AChR) between the intermediate and outer zone. Increased muscle tone was attributed to a disturbed neural influence, while increased CK activity was interpreted as being more characteristic for a primary muscle lesion. …