Charcot-Marie-Tooth Type 1A (CMT1A)/Hereditary Neuropathy with Liability to Pressure Palsies (HNPP), PMP22 Deletion/Duplication
Recommended test for suspected hereditary neuropathy with liability to pressure palsies (HNPP) and appropriate first-tier test for suspected Charcot-Marie-Tooth type 1 (CMT1) or CMT1A; does not detect sequence variants. Recommended test if there is a known familial PMP22 deletion or duplication previously identified in a family member.
Multiplex Ligation-dependent Probe Amplification
New York DOH Approval Status
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 1 mL)
Preferred transport temp: Refrigerated. Also acceptable: Room temperature.
Room temperature: 1 week ; Refrigerated: 1 month; Frozen: Unacceptable
BACKGROUND INFORMATION: Charcot-Marie-Tooth 1A (CMT1A)/ Hereditary Neuropathy with Liability to Pressure Palsies (HNPP), PMP22
CHARACTERISTICS: Charcot-Marie-Tooth disease, type 1A (CMT1A) is a subtype of CMT1, a hereditary neuropathy characterized by demyelinating progressive distal motor and sensory neuropathy, muscle weakness and atrophy, pes cavus foot deformity, and other findings. CMT1A is caused by duplication of the PMP22 gene. Hereditary neuropathy with liability to pressure palsies (HNPP) is a neurological disorder characterized by repeated focal
pressure neuropathies and peripheral neuropathy caused by deletion of the PMP22 gene.
INCIDENCE: CMT1A: 1/10,000; HNPP: 1/20,000-1/50,000.
INHERITANCE: Autosomal dominant; 10-20 percent of PMP22 duplications are de novo.
CAUSE: CMT1A is caused by a 1.5 Mb duplication at 17p11.2 including the PMP22 gene, while HNPP is caused by the reciprocal deletion of the same region.
CLINICAL SENSITIVITY: 70-80 percent for CMT1; 80 percent for HNPP.
METHODOLOGY: Multiplex ligation-dependent probe amplification (MLPA) of the PMP22 gene.
ANALYTICAL SENSITIVITY AND SPECIFICITY: 99 percent.
LIMITATIONS: Diagnostic errors can occur due to rare sequence variations. Single base pair substitutions, small deletions/duplications, regulatory region mutations, and deep intronic mutations are not detected. The breakpoints of large deletions/duplications are not determined.
This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the U.S. Food and Drug Administration. This test was performed in a CLIA-certified laboratory and is intended for clinical purposes.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2012161||Charcot-Marie-Tooth/HNPP DelDup Specimen||31208-2|
|2012162||Charcot-Marie-Tooth/HNPP DelDup Interp||35474-6|
- Hereditary Neuropathy
- Hereditary Neuropathy with liability to Pressure Palsies (HNPP)