Background
The neural cell adhesion molecule (N-CAM), also called CD56, is a cell-surface glycoprotein that mediates intercellular adhesive interactions in the nervous system. N-CAM is expressed in neuromuscular endplates, nerves, satellite cells, and embryonic muscle, but it is lost as development proceeds and is nearly absent from adult muscle. N-CAM re-expression was detected in a denervated, regenerating and degenerated muscle fibres. Muscle disease or myopathy is diagnosed based on the presence of denervated, regenerating and degenerated fibres on muscle biopsy combined with clinical information. Some regenerating fibres looked like normal fibre and were challenging to identify but showed positive N-CAM staining.
Objectives
To explore the expression of N-CAM in muscle disease.
Methods
N-CAM expression and interpretation were performed in a 3-year retrospective study of 75 muscle biopsies diagnosed with myopathies. The pathological findings and clinical information were also thoroughly reviewed.
Results
Of 75 myopathy patients, 41 (55%) cases were female, and 34 (45%) cases were male. The mean age was 35 years. The range of age was 3 months to 83 years. The expression of N-CAM and clinical information, including pathological findings, were analyzed using Fisher’s exact versus chi-square tests. N-CAM expression data was performed in 75 samples, 35 (46.67%) were positive for N-CAM, and 40 (53.33%) were negative for N-CAM. The diagnosis of the muscle disease was nonspecific myopathy with 35 (46%) cases, inflammatory myopathy with 17 (23%) cases, neurogenic myopathy with 9 (12%) cases, muscular dystrophy with 7 (9%) cases, non-diagnostic myopathy with 5 (7%) cases, and mitochondrial myopathy with 2 (3%) cases. The inflammatory myopathy showed positive N-CAM in 15 out of 17 cases with statistical significance (p-value < 0.001, ORs (95% CI) 14.250 (2.960-68.606)). N-CAM was also positive in muscular dystrophy, neurogenic myopathy, and nonspecific myopathy but was not statistically significant in p-value. No positive N-CAM was found in mitochondrial myopathy and non-diagnostic myopathy.
Conclusion
N-CAM expression accompanied by the pattern of staining could be considered to help narrow down the differential diagnosis of myopathies. We recommend further study in a larger group.