Laboratory Test Information Guide

Details for Charcot Marie Tooth Disease

Test Name: Charcot Marie Tooth Disease
Alternate Name(s): CMT
Charcot Marie Tooth Neuropathy Type 1A, 1B, 2A, 2B, 2K,X
Laboratory: Molecular Diagnostics
Specimen Type: Whole blood-2 x 4 mL Lavender EDTA top Vacutainer tube
Collection Information: Blood samples must be maintained at room temperature.
Requisition: MOLECULAR DIAGNOSTIC REQUISITION
Test Schedule: Monday-Friday
0800-1600 h
Turnaround time from when specimen
is received in testing laboratory:
 
Routine
3 months
Stat
 
 
Reference Range: See report
Effective Date: 2010-06-16
Revised Date: 2016-03-21
Critical Value:  
Interpretive Comments: CMT-Type 1

Disease characteristics:
Charcot-Marie-Tooth-neuropathy type 1 (CMT1) is a demyelinating peripheral neuropathy characterized by distal muscle weakness and atrophy, sensory loss, and slow nerve conduction velocity (NCV). It is usually slowly progressive and often associated with pes cavus foot deformity and bilateral foot drop. Affected individuals usually become symptomatic between 5 and 25 years of age. Fewer than 5% of individuals become wheelchair dependent. Life span is not shortened.

CMT1A represents 70-80% of all CMT1 and involved abnormalities of the PMP22 gene. About 98% of individuals with CMT1A have a duplication of PMP22 and this screening test is available at LHSC
CMT1B (5-10% of all CMT1) is associated with point mutations in LITAF (SIMPLE) gene.
CMT1E (<5% of all CMT1) is associated with point mutations IN PMP22.

It is requested that the clinician identify the specific gene(s) required to be analyzed based on the patients clinical and electrophysiological findings. It is recommended that any algorithm for CMT1 screening to be initiated with Chr. 17 duplication/duplication analysis.

Direct sequence analysis of specific genes known to be associated with certain CMT1 types including PMP22, MPZ, and the LITAF (SIMPLE) is available at the MDxL LHSC, .

Bird T. (2005) GeneTest: reviews.
Indicated gene to request: PMP22

CMT Type 2

Charcot-Marie-Tooth hereditary neuropathy type 2 (CMT2) is an axonal (non-demyelinating) peripheral neuropathy characterized by distal muscle weakness and atrophy, mild sensory loss, and normal or near-normal nerve conduction velocities. CMT2 is clinically similar to CMT1, although typically less severe. Peripheral nerves are not enlarged or hypertrohpic. There have been reported to be some fifteen subtypes of CMT2 which are similar clinically, and are distinguished by molecular genetic findings. The diagnosis of CMT type 2 is based on clinical findings and EMG/NCV characteristics.

It is requested that the clinician identify the specific gene(s) required to be analyzed based on the patients clinical and electrophysiological findings.

Direct sequence analysis of specific genes known to be associated with certain CMT2 types, including MFN2 (CMT2A), RAB7 (CMT2B), MPZ (CMT2I/CMT2J), and GDAP1 (CMT2K) is available at the MDxL LHSC, .

Bird T. (2005) GeneTest: reviews.
Indicated gene to request: MFN2, MPZ

CMT X-Linked

CMTX is characterized by a moderate to severe motor and sensory neuropathy in affected males and usually mild to no symptoms in carrier females. Sensorineural deafness and central nervous system symptoms also occur in some families.

Deleterious mutations affecting the GJB1 (C32) gene are reported to comprise 90% of the cases. Direct sequence analysis of the specific gene known to be associated with CMT X type (CX32) is available at the MDxL, LHSC


Bird T. (2005) GeneTest: reviews.
Indicated gene to request: CX32
Special Processing:  
Comments: For more information click on:
Method of Analysis: DNA Sequence Analysis
Critical Information Required:  
Storage & Shipment: Must be received in testing laboratory within 5 days of collection, shipped at room temperature by courier/overnight delivery.
System Codes: 
Cerner
 
 
Referred To:  

Questions? Comments? Contact Laura Gopaul