Congenital myopathy-10B (CMYP10B) is an autosomal recessive skeletal muscle disorder characterized by infantile- or childhood-onset myopathy, areflexia, dysphagia, and respiratory distress that usually requires nocturnal ventilation. Other common features include facial and neck muscle weakness, feeding difficulties, contractures, scoliosis, high-arched palate, hyporeflexia, and difficulties walking. The disorder is slowly progressive and most patients follow a chronic course. Muscle biopsy shows variable findings, including type 1 fiber predominance, minicore lesions, and myofibrillar disorganization (Boyden et al., 2012; Harris et al., 2018). Patients with missense mutations affecting conserved cysteine residues in the EGF-like domain show the mild variant phenotype (CMYP10B) with later onset of respiratory failure and minicores on muscle biopsy, whereas patients with more damaging mutations, including nonsense or frameshift null mutations, show the severe variant phenotype (CMYP10A) (Croci et al., 2022). For a discussion of genetic heterogeneity of congenital myopathy, see CMYP1A (117000). [from OMIM]