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©2013 UpToDate ® Print Email Genetics of CMT1, CTM2, and CMT3 Disorder Gene Chromosome Clinical features CMT1 Onset in first or second decade CMT1A PMP22 17p11.2-p1 Motor symptoms predominate (clumsy walking) Gradual loss of proprioception and vibration Ambulation usually maintained Normal life expectancy Palpable enlargement of the peripheral nerves NCV slowed to <60 percent normal CMT1B MPZ 1q22 CMT1C LITAF 16p.13.1-p12.3 CMT1D EGR2 10q21.1-q22.1 CMT1E PMP22 17p11.2-p1 CMT1F NEFL 8p21 Roussy-Levy MPZ 1q22 CTM1 features plus: Postural tremor and gait ataxia PMP22 17p11.2 CMTX1 GJB1 Xq13.1 CMT1 features plus: Symptoms more prominent in males Symptomatic in second decade Loss of ankle reflexes NCV moderately slowed CMT2 Onset in second or third decade CTM2A MFN2 1p36.2 Sensory symptoms predominate CTM2B RAB7 3q21.3 CMT2C TRPV4 12q24.1 CTM2D GARS 7p15 CMT2E NEFL 8p CMT2F HSPB1 7q11.23 CMT2G 12q12-q13 CMT2I MPZ 1q22 CMT2K GDAP1 8q13-q21.1 CMT2L HSPB8 12q24.23 Early onset Not known Onset before age 5 years Rapid progression of weakness below the knee Loss of ambulation by mid-teens NCV normal or mildly reduced CMT3 Severe, early onset Dejerine-Sottas syndrome PMP22 17p11.2-p1 Hypotonia in early infancy Delayed motor development Initial sensory loss and distal weakness Ataxia NCV profoundly slowed (10m/sec) MPZ 1q22 EGR2 10q21.1-q22.1 Congenital hypomyelinating neuropathy PMP22 17p11.2-p1 Profound hypotonia and contractures at birth Feeding difficulties Respiratory distress Death in infancy NCV extremely slowed or absent MPZ 1q22 EGR2 10q21.1-q22.1