There are six main types of congenital myopathy, but other rare types have also been identified. The different types vary in symptoms, severity, treatment options and outlook.
The six main types of congenital myopathy are:
Central core disease is a type of core myopathy. Core myopathies are the most common type of congenital myopathy. Typically, floppiness (hypotonia) is seen in infants. Children have delayed milestones and moderate arm and leg weakness. However, weakness doesn’t seem to worsen over time. A change (mutation) in the RYR1 gene causes central core disease.
Minicore (multicore) disease is another type of core myopathy. It has many subtypes. Most subtypes include severe weakness in the arms and legs. Scoliosis (spine curve) is also frequently seen. Breathing difficulties are common, and weakened eye movements can occur. A mutation in the RYR1 gene or another gene causes multicore disease.
Nemaline myopathy is another common congenital myopathy. Babies with nemaline myopathy typically have breathing problems and feeding issues. They also frequently have weakness in their face, neck, arms and legs. In addition, skeletal complications such as scoliosis can occur. A mutation in one of several genes, including NEM2, ACTA1 andTPM2, causes nemaline myopathy.
Centronuclear myopathy is a very rare congenital myopathy. Symptoms include weakness in your baby’s arms, legs and face, droopy eyelids and problems with eye movement. Weakness tends to worsen over time. A mutation in the DNM2, BIN1 or RYR1 gene causes centronuclear myopathy.
Myotubular myopathy is a rare kind of congenital myopathy that usually only affects male babies. Floppiness and weakness are very severe. Breathing and swallowing difficulties are common. A condition called osteopenia (weak bones) is common as well. Many children don’t survive their first year of life. A mutation in the MTM1 gene causes myotubular myopathy.
Congenital fiber-type disproportion myopathy is a rare condition that starts with floppiness. Symptoms include face, arm and leg weakness along with breathing difficulties. Most infants are severely affected, but their respiratory function can improve with age. Mutations in the TPM3 gene, ACTA1 gene, TPM2 gene, MYH7 gene and RYR1 gene have been found in children with congenital fiber-type disproportion myopathy.