Central core disease is a congenital myopathy defined by the presence on muscle biopsy microscopy of numerous muscle fibers that lack oxidative activity, thus making "cores" on NADH-stained slides within muscle fibers. Reported to be one of the most frequent forms of congenital myopathy, this disease usually becomes apparent in infancy or childhood. Facial, neck, and proximal limb weakness with generalized hypotonia are the characteristic clinical features; but phenotypic severity is widely variable. The disease is linked to a ryanodine receptor gene mutation (RYR1, chromosome 19q13). The ryanodine receptor is depicted in the illustration. Malignant hyperthermia is highly associated with central core disease, independent of the degree of muscle weakness.
(Main source: Mark Cohen's chapter in Prayson's Neuropathology, A volume in the Foundations in Diagnostic Pathology series, first edition)