[Muscle biopsy in the neonatal and perinatal period: a retrospective study of 535 cases]. / Biopsie musculaire en période néonatale et périnatale - Une évaluation rétrospective de 535 cas.

Neuromuscular diseases with neonatal or perinatal onset are usually very severe. Their diagnosis requires rigorous studies in order to determine the cause of the disease and thus help to establish the vital prognosis. Neonatal muscle biopsy studies are driven by the extreme severity of the clinical picture. The aim of this analysis is to search for or validate a precise diagnosis and etiology. Numerous genes are at the origin of these severe neonatal myopathies, for some of them anomalies of a specific gene could be identified.

Loss of Sarcomeric Scaffolding as a Common Baseline Histopathologic Lesion in Titin-Related Myopathies.

Titin-related myopathies are heterogeneous clinical conditions associated with mutations in TTN. To define their histopathologic boundaries and try to overcome the difficulty in assessing the pathogenic role of TTN variants, we performed a thorough morphological skeletal muscle analysis including light and electron microscopy in 23 patients with different clinical phenotypes presenting pathogenic autosomal dominant or autosomal recessive (AR) mutations located in different TTN domains. We identified a consistent pattern characterized by diverse defects in oxidative staining with prominent nuclear internalization in congenital phenotypes (AR-CM) (n = 10), ± necrotic/regenerative fibers, associated with endomysial fibrosis and rimmed vacuoles (RVs) in AR early-onset Emery-Dreifuss-like (AR-ED) (n = 4) and AR adult-onset distal myopathies (n = 4), and cytoplasmic bodies (CBs) as predominant finding in hereditary myopathy with early respiratory failure (HMERF) patients (n = 5). Ultrastructurally, the most significant abnormalities, particularly in AR-CM, were multiple narrow core lesions and/or clear small areas of disorganizations affecting one or a few sarcomeres with M-band and sometimes A-band disruption and loss of thick filaments. CBs were noted in some AR-CM and associated with RVs in HMERF and some AR-ED cases. As a whole, we described recognizable histopathological patterns and structural alterations that could point toward considering the pathogenicity of TTN mutations.