SELENON and congenital muscular dystrophy: Mutations in SEPN1 are also responsible for a congenital muscular dystrophy characterized by marked spinal rigidity (rigid spine muscular dystrophy, RSMD), and patients with multiminicore myopathy associated with selenoprotein N deficiency can present clinical features that partially overlap with those of RSMD patients, such as early-onset spinal rigidity and respiratory failure [77].