Congenital Myopathies

These are the non-dystrophic congenital myopathies

Nemaline myopathy a.k.a. nemaline rod myopathy:

Clinical features:

Floppy infant with facial weakness and respiratory insufficiency.
Also see adult from a.k.a. sporadic late onset nemaline myopathy


Autosomal dominant, autosomal recessive
Mutations in the following Proteins:

  • Alpha-skeletal actin
  • Nebulin
  • Troponin.
Muscle biopsy:

HE fibre atrophy without grouping, subsarcolemmal increased eosinophilic staining. GMT subsarcolemmal purple/red nemaline rods in type 1 fibres. Often type 1 fibre hypertrophy, type 1 fibre predominance.
EM: nemaline rods= osmiophilic rods
Immunohistochemistry: Alpha actinin type 2 positive rods in a lot of cases,
Note: nemaline rods can occur in inflammatory muscle disease and in central core disease.
Also see adult from a.k.a. sporadic late onset nemaline myopathy.

Centronuclear myopathy a.k.a. myotubular myopathy:

A group of genetic disorders: infantile (X linked), childhood (autosomal dominant, autosomal recessive), adult (autosomal dominant)

Muscle biopsy:

Type 1 fibres: Central nuclei and small. Normal type 2 fibres usually.
Type 1 fibre predominance.

Central core disease:

Clinical features:

Floppy infant: hypotonia
Childhood and adults. Proximal weakness, neck flexors and facial muscles. Associated with skeletal abnormalities scoliosis, developmental dysplasia of the hip


A group of disorders:

  • Autosomal dominant,
  • Rarely recessive (multiminicore disease)
  • RYR1 gene ryanodine receptor mutation (Ca++ channel).
Muscle biopsy:

Type 1 fibres: central area devoid of staining with NADH, also devoid of staining with SDH and COX
Strong Type 1 fibre predominance.
Myopathic features may occur
EM: central areas devoid of mitochondria extending the full length of the muscle fibre

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