Coexistence of minicores, cores, and rods in the same muscle biopsy. A new example of mixed congenital myopathy.

The authors report on the ultrastructural study of a muscle biopsy carried out in a child 6 years after the first biopsy which had led to diagnosis of "multicore disease". Clinical evolution following a few years of muscular involvement had been favorable. The lesions observed in the second biopsy were again characterized by the presence of multicores, but in addition to cores and rods. All of these abnormalities could sometimes be noted in a single muscle fiber. Although rare cases of an association of two types of lesions have been reported, no study has hitherto shown multicores, cores, and rods in the same biopsy. This observation might confirm the possibility of common pathogenic mechanisms producing these lesions.