Central Core Disease (CCD)
A rare, nonprogressive myopathy often present at infancy, which is characterized by hypotonia and proximal muscle weakness. In most cases. CCD has been linked to mutations in the RyRI gene encoding the Ca2+ release channel of the sarcoplasmic reticulum. Diagnosis is made on the basis of the lack of mitochondria and oxidative enzyme activity in central regions of skeletal muscle cells, observed upon histological examination of muscle biopsies.