Megaconial congenital muscular dystrophy (CMD) (OMIM#60251) is a rare form of congenital muscular dystrophy characterised by early onset of floppiness (low muscle tone or hypotonia as explained by the doctor), muscle weakness with delay motor development, global developmental delay, and intellectual disability with learning difficulty. Many of the affected children also have autistic features. Structural brain abnormalities are usually absent. Some patients also develop cardiomyopathy, a type of heart disease with weakened heart muscles causing heart dysfunction. The presence of cardiomyopathy increases the risk of early death. Other patients have ichthyosis-like skin changes.
For the affected children who have a severe presentation with marked muscle weakness, they will be unable to sit, stand or walk. They may also have marked learning difficulty and significant behavioral problems with autistic features and unable to communicate with speech. Other children with a milder presentation have delayed in walking and delayed in speech development. They will walk with wide-based waddling gait. As the muscle weakness usually slowly progress over time, some of them may loss ambulation at a later age.
Blood test often reveals mild to moderate elevation of a muscle enzyme called Creatine Kinases. Examination of the skeletal muscle obtained from biopsy will show abnormal findings with evidence of variation in muscle fibre with muscle fibre degeneration and regeneration, and the appearance of giant mitochondria in the periphery of the muscle fibers but spared in the centre.
CHKB