Myopathy with multiple minicore--report of two siblings.

Two cases of non-progressive congenital hypotonia are described in siblings, male and female, aged 5 and 9 years, respectively, which morphologically correspond to myopathy with multicore or minicore. The study of these 2 cases is compared with those described in the literature, with special emphasis on the analysis of the histochemical picture. The disease in all the cases is defined by the presence of multiple small foci of loss of cross striation with loss of activity of myofibrillar ATPase and oxidative enzymes. Furthermore, a predominance and hypotrophy of type I fibers and in some cases hypertrophy of type II is constantly recorded, which is interpreted as an alteration in muscle maturation. We review other myopathies described with focal loss of cross-striation which associate central nuclei with the myofibrillar lesion, considering them to be myopathy with multicore or minicore.