ACTA1 and nemaline myopathy: Through in-depth histological, ultrastructural, and immunofluorescence investigations of the ten new and three published cases, we expand the spectrum of morphological muscle anomalies in severe ACTA1-related NM, and we also provide a potential disease signature encompassing intranuclear rods, cytoplasmic bodies, neuromuscular junction abnormalities, and the enlargement of the perinuclear space.