Like many of the congenital myopathies, the features of central core disease tend to be more severe course if the disease initially presents in infancy.  A more moderate expression of the disease is expected if it presents in childhood, and the disease relatively mild if it first becomes apparent when the patient is an adult.

Distinguishing Clinical Features

Patients with central core disease (CCD) are at risk to develop malignant hyperthermia upon exposure to general anesthesia or certain induction agents.

The course of CCD may be slowly progressive at first, but this is often followed by a period during which clinical improvement occurs.

Central core disease is associated with an autosomal dominant inheritance pattern.  The most common genetic  cause of the disease is linked to a mutation in the gene that codes for the ryanodine receptor (RYR-1).

Pathologic Findings

The defining pathologic feature is the presence of cores within muscle fibers.  Cores are round or cylindrical blobs within fibers which are clearly visible with many common staining techniques.  

Here are some examples (click to enlarge):

The cores, which appear as pale blobs on stains for NADH or COX (the images above), are regions which have no mitochondria, and which may or may not have intact myofbrillary architecture.  The lack of mitochondria (and therefore lack of oxidative activity) is the reason the blobs look pale on NADH or COX staining.

Another common feature of CCD is that there is often a predominance of type 1 fibers compared to type 2 fibers.  This finding can be seen in other disorders, and is not exclusive to CCD.  The ATPase-stained image below does not demonstrate any cores, but does highlight the preponderance of type 1 fibers (click to enlarge):

Central cores need to be distinguished from target fibers, which may appear very similar.  Target fibers are a common finding in cases of denervation, and represent restructuring within the musle fiber.  There is also a dearth of mitochondria in the center of target fibers.  However, these represent recent denervation, and not myopathy.  An example of target fibers is shown in the image below (click to enlarge):

Management

Recommended management is aggressive supportive care.  Functional improvement is common.

References:

Katirji, B., Kaminsky, H.J., Preston, D.C., Ruff, R.L., and Shapiro, B.E. (Eds.) (2002). Neuromuscular Disorders in Clinical Practice. Butterworth Heinemann, Boston. (ISBN:0750671696)  Pp. 1114-1127.

Prayson, R.A., and Goldblum, J.R. (Eds.) (2005). Neuropathology. Elsevier Churchill Livingstone, Philadelphia. (ISBN:0443066582)  Pp. 537-581.

Jungbluth H. Central core disease. Orphanet Journal of Rare Diseases. 2, 25. 2007. doi:10.1186/1750-1172-2-25. (PMID:17504518).