muscle weakness

This is a progressive disorder in which psychomotor regression and loss of speech develop by 1 to 2 years of age, often appearing as the first sign of abnormalities.  Cognitive impairment can progress to profound intellectual disability.  Older patients have limb and truncal ataxia and experience frequent falls.  Muscle tone in the limbs is increased and children often exhibit dyskinesia, dystonia, and axial hypotonia.  General muscle weakness is often present.  No abnormalities have been seen on brain imaging.

Some patients develop a nephropathy with renal insufficiency, hypertension, and hyperechogenic kidneys though deterioration of the renal disease is slow.  Renal biopsy in one patient revealed tubulointerstitial nephritis but no individuals have reached end-stage renal failure.

Charcot-Marie-Tooth disease is a large group of clinically and genetically heterogeneous disorders characterized by progressive motor and sensory polyneuropathy.  These can be separated (with overlap) into two large groups on the basis of electrophysiologic criteria: type 1 is the demyelinating form, and type 2 the axonal form.  Patients with primarily distal motor neuropathy are sometimes considered to comprise a third type.

 Symptoms such as weakness in the extremities and digits have a variable age of onset but usually become evident in late childhood or early adulthood.  Small muscles of the hands and feet are often atrophied to some degree.  Some patients develop hearing loss of the neurosensory type.  Foot deformities such as pes cavus are common.  Nerve conduction velocity (reduction) and electromyography can be helpful diagnostically.  It may be helpful to look for characteristic changes such as loss of myelinated fibers and focal myelin sheath folding in sural nerve biopsies.  Intellectual impairment and dementia are usually not features of Charcot-Marie-Tooth disease.

Hemizygous individuals with X-linked types of CMT such as CMTX2-5 seem to be more likely to have intellectual disabilities, hearing loss, spasticity, and optic neuropathy.

Stiffness and weakness of the lower limbs begins between 2 and 20 years of age.  This is slowly progressive although most individuals are still mobile with mild to moderate handicaps into the 4^th decade.  The gait is spastic with weakness, hyperreflexia, and extensor plantar responses in the lower limbs.  The upper limbs are variably involved and movements are dysmetric.  Dysarthria and bladder dysfunction are often present.  Cerebellar ataxia is common and some patients first present with this as a prominent sign in the first and second decades.  Early cognitive development is normal but mild cognitive decline appears eventually.  Pes cavus and scoliosis may occur.

Brain imaging can show thinning of the corpus callosum, with mild cerebellar and cerebral atrophy.

Psychomotor development is initially normal but signs of delay are usually present during the first year of life.  Patients may be able to walk but only with support.  Pyramidal and cerebellar dysfunction, muscle weakness and wasting, dysarthria, truncal hypotonia, intention tremor, and spasticity are evident during the first decade.  Some have seizures.  Cognitive impairment ranges from mild to moderate.  Most patients become wheelchair-bound late in the first decade of life and some do not survive beyond childhood.

Hypomyelination and mild axonal loss may be seen in peripheral nerve biopsies while neuroimaging shows evidence of diffuse and progressive cerebral white matter atrophy.

This disorder, originally believed to be a type of glycogen storage disease, is actually a form of autophagic vacuolar myopathy.    The characteristic vacuoles are found in muscle cytoplasm surrounded by sarcolemmal proteins and basal lamina.  The primary extraocular disease occurs in the myocardium although skeletal muscle may also be involved.  Intellectual disability is a variable and inconsistent feature.  

Cardiac rhythm abnormalities are common and include AV nodal block, atrial fibrillation, and Wolff-Parkinson-White EKG findings.  Hypertrophic cardiomyopathy (and sometimes dilated cardiomyopathy) with primary involvement of the left ventricle is common.  Symptoms typically occur in males before the age of 20 years and somewhat later in females.

Some patients have muscular weakness and exercise intolerance.  Diagnosis can be made when the characteristic vacuoles are present in a muscle biopsy but their absence does not rule out the diagnosis.