congenital myopathy 1A

A congenital myopathy that is characterized by muscle weakness primarily affecting the proximal muscles of the lower limbs beginning in infancy or early childhood, although later onset of symptoms has been reported and that has_material_basis_in heterozygous m

A congenital myopathy that is characterized by muscle weakness primarily affecting the proximal muscles of the lower limbs beginning in infancy or early childhood, although later onset of symptoms has been reported and that has_material_basis_in heterozygous mutation in the ryanodine receptor-1 gene (RYR1) on chromosome 19q13. Heterozygous mutation in the RYR1 gene also causes susceptibility to malignant hyperthermia-1 (MHS1), patients with CMYP1A are at risk for MHS. Biallelic mutations in the RYR1 gene cause autosomal recessive CMYP1B, which shows overlapping features, but is typically more severe.

Signs and symptoms

• Muscle weakness
• Centrally nucleated skeletal muscle fibers
• Delayed ability to walk
• Feeding difficulties
• Central core regions in muscle fibers
• Neonatal hypotonia
• Nemaline bodies
• Increased variability in muscle fiber diameter
• Weakness of facial musculature
• Hyporeflexia

Also known as: autosomal dominant congenital myopathy 1A; central core disease; central core myopathy