Some hereditary myopathies can mimic acquired polymyositis (PM) in particular when they first present in adulthood with a limb-girdle distribution of weakness. The diagnosis is made yet more complex when inflammatory infiltrates attend on muscle biopsy. This is common in certain dystrophies in particular limb-girdle muscular dystrophies (LGMD). For better distinction between the two diseases, histochemical morphometric analysis for twenty biopsies of proteomically confirmed LGMD and eight PM biopsies was performed. Each parameter of myopathy was evaluated in five or ten randomly, selected fields, using Image-Pro plus bioanalytical software. Comparison between groups was tested using Student’s t-test analysis. The muscle of LGMD patients betrayed more splitting fibers and larger connective tissue surface area in comparison to PM patients (p = 0.02, 0.01, respectively). On the opposite, the number of regenerating fibers was higher in myositis biopsies (p = 0.04). Other parameters were akin to those of PM patients. We also described different patterns MHC-I up regulation on LGMD biopsies. We reported some tips of difference between LGMD biopsies and PM.
Key words: Limb-girdle muscular dystrophies (LGMD), polymyositis (PM), histocompatibility complex class I (MHC-I), morphometric.
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