Amniotic Fluid, Chorionic Villus Sample, Peripheral Venous Blood, Cord blood, Extracted DNA, Dry Blood Spot
Charcot-Marie-Tooth 1A/HNPP (PMP22, COX10, TEKT3) Deletion/Duplication Analysis
Test Overview
Charcot-Marie-Tooth disease type 1A (CMT1A) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) are inherited peripheral nerve disorders commonly associated with changes in the PMP22 gene. This genetic test detects large deletions or duplications involving the PMP22, COX10, and TEKT3 genes to help diagnose these neuropathies.
Why This Test Is Done
This test is recommended for individuals with:
- Progressive muscle weakness in the feet, legs, or hands
- Frequent numbness or tingling sensations
- Foot deformities such as high arches or hammertoes
- Difficulty walking or balance issues
- Recurrent nerve palsies triggered by pressure or minor injury
- Family history of hereditary neuropathy or CMT
Clinical Significance
-
PMP22 duplication is strongly associated with CMT1A, the most common inherited demyelinating neuropathy.
-
PMP22 deletion is linked to HNPP, a disorder causing recurrent focal nerve palsies and sensory symptoms.
- The analysis may also evaluate neighboring genes such as COX10 and TEKT3, which can be involved in larger chromosomal rearrangements.
Methodology
Testing is typically performed using advanced molecular techniques such as:
- MLPA (Multiplex Ligation-dependent Probe Amplification)
- Copy Number Variation (CNV) analysis
- PCR-based deletion/duplication studies
These methods help identify abnormal copy numbers of the target genes.
Sample Required
Preparation
- No fasting or special preparation required.
Interpretation
-
Positive Result: Indicates a pathogenic deletion or duplication associated with CMT1A or HNPP.
-
Negative Result: Does not completely rule out hereditary neuropathy, as other gene mutations may be involved. Further genetic testing may be advised.
Who Should Consider This Test?
- Individuals with unexplained peripheral neuropathy
- Patients with abnormal nerve conduction studies
- People with family history of CMT or HNPP
- Individuals experiencing recurrent pressure-related nerve injuries
Turnaround Time
- Usually 2–4 weeks, depending on the laboratory.
Important Note
Genetic counseling is recommended before and after testing to help understand the results, inheritance patterns, and implications for family members.
