Histopathology of<unk> 2. Muscle biopsy showing mild myopathic changes and grouping of atrophic fast fibres (type 2, highlighted). Immunohistochemical staining for type-1 ("slow") myosin. Molecular Mutations of<unk> 1 and<unk> 2 cause production of RNA that sequesters RNA-binding proteins, causing dysregulated RNA splicing. This dysregulated RNA splicing is particularly toxic to skeletal, cardiac, and smooth muscle. One example in<unk> 1 involves the chloride channel ClC-1. Mutated<unk> PK RNA binds to MBNL1, causing ClC-1 pre-mRNA to be spliced into the fetal form instead of the adult form. Functional loss of the chloride channel causes<unk> . Histology In<unk> 1, there can be increased central nuclei, angular fibers, fiber atrophy, and pyknotic clumps. There can be selective atrophy of type 1 muscle fibers. Muscle fibers show signs of degeneration and regeneration. There is modest fibrosis of the endomysium. In<unk> 2, there can be variation in the sizes of muscle fibers, although often there are no abnormalities. There is selective atrophy of type 2 muscle fibers. Again, there are central nuclei and nuclear clumps.
Myotonic dystrophy
Prader–Willi syndrome
Becker muscular dystrophy
Myotonia congenita
Muscular dystrophy
Ullrich congenital muscular dystrophy
Madras motor neuron disease
Infantile neuroaxonal dystrophy