Common origin of rods, cores, miniature cores, and focal loss of cross-striations.

Twelve patients suffering from congenital neuromuscular disorders showed at least two of the following structural changes in their muscle biopsy specimens: rods, cores, miniature cores (M lesions), and focal loss of cross-strians (F lesions). There appeared to be no essential differences between M and F lesions except for the presence of vesicular nuclei in and around the latter. A striking finding was the presence of adjacent M lesions, F lesions, or both in two or several adjoining muscle fibers. Serial sections often showed a definite relationship of the lesions with blood vessels. The finding of rods cores, and M and F lesions, not only in one biopsy specimen but also in one muscle fiber, raised the intriguing possibility of common pathogenic mechanisms producing these lesions.