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new test for CMT and a bit of history (2001) by Susan Ulisse, Athena Diagnostics Marketing Assistant Athena Diagnostics offered our first CMT test in 1993. Since then, collaboration with academic and clinical researchers has allowed Athena to develop and commercialize a comprehensive range of genetic test for CMT, including testing for the PMP22, EGR2, MPZ, and Connexin32 genes. Continuing in this tradition, we are pleased to announce the recent development of testing services for the neurofilament-light gene (NF-L) involved in Charcot-Marie-Tooth disease type 2 (CMT2). A variety of disease-causing mutations in the NF-L gene are associated with this axonal form of CMT. To provide a more accurate diagnosis, Athena sequences the entire coding region of the NF-L gene in order to detect these mutations.1 Historically, Charcot-Marie-Tooth disease has been divided into two subcategories: CMT type 1 (CMT1) and CMT type 2 (CMT2) on the basis of nerve conduction velocities (NCV). CMT1 is typically the demyelinating form of the disease and is characterized by a considerable decrease in motor and sensory NCVs, with an upper limit of 38 m/s for the motor NCV of the median nerve.2 By contrast, CMT2 is an axonal peripheral neuropathy and is characterized by an NCV that is only slightly decreased (>38 m/s) or even normal.2 CMT2 is usually inherited in an autosomal dominant fashion (meaning there is a 50% chance that the children of an individual with a CMT mutation will be affected with the disorder). NF-L is the first gene discovered in CMT2. A missense mutation (a mutation that causes substitution of one amino acid for another, resulting in a different sequence) in the NF-L gene (NEFL) on chromosome 8p21 is linked to the disease.3 The NF-L gene encodes neurofilament light protein, which is one of the three major neurofilament proteins constituents. Neurofilaments play an important role in axonal structure. Two leading CMT research groups studied families with CMT2 caused by neurofilament light gene mutation. These families demonstrated the clinical presentation and genotype of CMT2. In the first study, Irina V. Mersiyanova et al., suggest that Gln333Pro represents a rare disease-causing mutation, which results in the CMT2 phenotype.4 Vincent Timmerman, PhD, Peter De Jonghe, MD, PhD et al. identified a novel mutation, Pro8Arg, in a second CMT family.5 Because of overlapping clinical symptoms with other inherited peripheral neuropathies, CMT may be challenging to diagnose clinically, and CMT2 may be difficult to distinguish from other forms of CMT, such as CMT1, CMTX, and chronic idiopathic axonal neuropathy.6 A genetic test can help clarify a clinical diagnosis and provide the most accurate information about an individual's CMT type, which may help in assigning risks for developing the disease or passing on the abnormal gene to family members, enable appropriate genetic counseling, and lead to better disease management. To learn more about Athena's CMT full line of testing, visit:
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