North et al listed criteria for the diagnosis of congenital nemaline myopathy. The authors are from the ENMC International Consortium on Nemaline Myopathy.


Inheritance: autosomal recessive or dominant


Onset: may be during infancy, childhood or as an adult


Patterns of muscle weakness (usually with sparing of the extraocular muscles)

(1) predominantly proximal limb muscles, neck muscles and diaphragm

(2) diffuse, involving both proximal and distal muscles

(3) selective muscle groups (scapularhumeral, scapuloperoneal)

(4) facial with any of the above


Nerve conduction findings:

(1) normal sensory amplitudes, velocities and latencies

(2) normal motor conduction velocities and latencies

(3) with distal atrophy the muscle action potential amplitudes may be decreased


EMG findings:

(1) may be normal early

(2) may show a myopathic pattern early

(3) may show a neuropathic pattern in distal muscles with late disease


Laboratory findings:

(1) normal or mildly elevated serum CK

(2) nemaline bodies (rods) seen

(2a) with light microscopy in Gomori trichrome stains in the subsarcolemmal or sarcoplasmic regions

(2b) with light microscopy in immunostains of alpha-actinin

(2c) with electron microscopy (resemble Z disc with periodic lattice pattern)


Molecular findings:

(1) NEM1 at 1q22-q23: in autosomal dominant form

(2) NEM2 at 2q21.2-2q22): in autosomal recessive form

(3) TPM3 (alpha tropomyosin): in autosomal dominant form


Exclusion criteria:

(1) sensory involvement

(2) a condition associated with acquired nemaline myopathy


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