A retrospective study of 535 muscle biopsies taken over 52 years from infants aged between 0 and 6 months and collected at the Institut de Myologie showed that :
- 82% of them showed abnormalities specific to a neuromuscular disease;
- between 1970 and 1999, 11.6% of biopsies (out of 248) were normal, compared with 4% (out of 287) between 2000 and 2021, as improvements in microscopy techniques and imaging software, together with the availability of antibodies, have enabled smaller histological lesions to be detected;
- of the 94 cases of congenital myopathy, genetic studies have identified the causal gene in 61% of cases, 80% of which occurred between 2000 and 2021;
- the causal gene was identified in only 19% of metabolic myopathies;
- the 120 electron microscopy studies concerned patients with congenital myopathies (62%), metabolic myopathies (22%), motor neuron or neuromuscular junction lesions (6%) or muscular dystrophies (6%).
With the advent of new-generation sequencing techniques (NGS), morphological analysis of muscle biopsies is now carried out alongside genetic analysis, providing additional information.
