[Pathomorphological characteristics of inflammatory and hereditary myopathies]

To characterize the immunophenotypic features of the inflammatory infiltrate cell composition and the morphometric features of muscle fibers in skeletal muscle biopsies from patients with hereditary and inflammatory myopathies, and to develop an integral coefficient to aid in the differential diagnosis of these conditions.

The material is represented by biopsy specimens of m. tibialis anterior, m. vastus lateralis, m. gastrocnemius med, m. peroneus longus et brevis, m. deltoideus, m. biceps femoris and m. latissimus dorsi of patients with polymyositis (n=7), dermatomyositis (n=3), dysferlinopathy (n=10) and calpainopathy (n=3), established on the basis of molecular-genetic, clinical-instrumental and morphological data. All biopsies underwent pathohistological and immunohistochemical examination.

The number of necrotic muscle fibers was significantly higher in polymyositis compared to dermatomyositis (p=0.008), dysferlinopathy (p=0.003), and calpainopathy (p=0.009), showing a diffuse pattern. In dermatomyositis, necrotic muscle fibers were predominantly perifascicular. In dysferlinopathy, a positive correlation between CD68⁺-macrophages and CD4⁺-T-helpers in the perimysium (p=0.04) were observed. The number of CD8⁺-T-killer cells invading muscle fibers was higher in polymyositis compared to dysferlinopathy (p=0.034). Increased numbers of CD138⁺-plasma cells was also noted in polymyositis. The MICE coefficient was lower in hereditary myopathies.

Immunophenotyping of the inflammatory infiltrate and quantitative morphometry using the integral MICE coefficient provide criteria for the differential diagnosis of myopathies of different origins. The established differences in the cellular composition of the infiltrate (particularly, the predominance of invasion by CD8⁺-T-killers in polymyositis) and in the degree of morphological homogeneity of muscle fibers (higher in hereditary forms) represent objective differential diagnostic criteria. Thus, the integrated application of these approaches can significantly improve the accuracy of verifying the differential diagnosis in myopathies of various origins.