Table 18.1 Nomenclature of bone tumors

Charcot-Marie-Tooth disease

BASIC INFORMATION
DEFINITION
Charcot-Marie-Tooth (CMT) disease is also called peroneal muscular atrophy. CMT describes the common clinical phenotype (1 in 2500 persons), distal limb wasting and weakness that slowly progresses over many years, mostly in the legs, with variable loss of sensation and reflexes. In advanced disease, distal wasting is so marked that the legs are said to resemble inverted champagne bottles. Mild cases have pes cavus and toe clawing that can pass unnoticed. Multiple genetic variants of the CMT phenotype are recognized, e.g.:
■ HSMN Ia (CMT 1A) - the commonest (70% of CMT; 1:2500 births), autosomal dominant demyelinating neuropathy caused by duplication (or point mutation) of a 1.5 megabase portion p11.2 of chromosome 17 encompassing the peripheral myelin protein 22 gene (PMP-22, 17p11.2).
■ HSMN Ib (CMT 1B) - the second commonest, an autosomal dominant demyelinating neuropathy due to mutations in the myelin protein zero gene (MPZ) on chromosome 1 (1q22).
■ HSMN II (CMT 2) - rare axonal polyneuropathies also caused by MFN2 or KIFIB on chromosome 1p36 and other mutations. There is prominent sensory involvement with pain and parasthesias.
■ Distal spinal muscular atrophy - a rare cause of CMT phenotype.
■ CMT with optic atrophy, deafness, retinitis pigmentosa and spastic paraparesis.
■ CMTX is an X-linked dominant HSMN on chromosome Xq13.1. The gene product is a gap junction B1 protein (GJB1) or connexin 32
SYNONYMS
Peroneal muscular atrophy
Hereditary motor and sensory neuropathy (HMSN)
Idiopathic dominantly inherited hypertrophic polyneuropathy
EPIDEMIOLOGY & DEMOGRAPHICS
PREDOMINANT AGE: Onset usually 10 to 20 years but can be delayed to 50 to 60 years
PREDOMINANT SEX: Male:female ratio of 3:1

Table 44. FORMS OF CHARCOT-MARIE-TOOTH DISEASE

PHYSICAL FINDINGS & CLINICAL PRESENTATION
• Variable presentation from family to family, but affected individuals in a family tend to have similar symptomatology
• Usually, gradual onset, with slowly progressive disorder
• Foot deformity producing a high arch (cavus) and hammer toes
• Atrophy of the lower legs producing a stork-like appearance (muscle wasting does not involve the upper legs)
• Nerve enlargement
• Sensory loss or other neurologic signs, although the sensory involvement is usually mild
• Scoliosis
• Decreased proprioception that often interferes with balance and gait
• Painful paresthesias
• In late cases, possible involvement of hands
• Absence of DTRs in many cases
• Poorly healing foot ulcers in some patients

ETIOLOGY
Chronic segmental demyelination of peripheral nerves with hypertrophic changes caused by remyelination
DIAGNOSIS
DIFFERENTIAL DIAGNOSIS
• Other inherited neuropathies
• Toxic, metabolic, and nutritional polyneuropathies
WORKUP
• The early onset, slow progression, and familial nature of the disorder are usually sufficient to establish diagnosis.
• Electrophysiologic studies are often diagnostic and may also be helpful in defining various subtypes of this group of neuropathies.
• Occasionally, muscle and nerve (sural) biopsy may be required.
TREATMENT

ACUTE GENERAL Rx
• Genetic counseling
• Supportive physical therapy and occupational therapy
• Prevention of injury to limbs with diminished sensibility
• Bracing
CHRONIC Rx
Occasionally, surgery to add stability and restore a plantigrade foot
DISPOSITION
• Disability is usually mild and compatible with a long life.
• 12% to 24% of patients are asymptomatic.
• A small number of cases are nonambulators by the sixth or seventh decade.
REFERRAL
• For orthopedic consultation for bracing and treatment of deformity
• For genetic counseling