10-year-old boy has increasing muscle weakness and raised CPK levels. The most likely defect is in plasma membrane of
A. NervesB. Muscle fibers
C. Basement membrane
D. All body cells
Answer .B. Muscle fibers
Several
lysosomal enzymes are released by damaged or degenerating muscle fibers and may
be measured in serum.
• The most useful these enzymes
is the creatine kinase (CK), which is found in only three organs and may be
separated into corresponding isozymes: MM for skeletal muscle, MB for cardiac
muscle, and BB for brain.
• Serum CK determination is by
no means a universal screening test for neuromuscular disease because many
disease of the motor unit may not be associated with elevated enzymes.
• However, the CK level is
characteristically elevated in certain diseases, such as Duchenne muscular
dystrophy, and the magnitude of increase is characteristic for particular
disease.
