Charcot-Marie-Tooth Disease, Type 1A: PMP22 MLPA

Test Information

PMP22 MLPA is a molecular test used to identify deletions or duplications in the gene associated with Charcot-Marie-Tooth Disease Type 1A.

Turnaround Time

3 weeks

CPT Code(s)

81324

Cost

$500

Genes

Clinical Information

Charcot-Marie-Tooth (CMT) disease is the most common form of inherited peripheral neuropathy, and these conditions have a prevalence of approximately 1 in 3000 individuals. Clinical symptoms include distal muscle weakness with atrophy, loss of deep tendon reflexes, high-arched feet, and loss of sensation. These conditions tend to be progressive, and while most families demonstrate autosomal dominant inheritance, autosomal recessive and X-linked inheritance also occurs. Symptoms and age of onset are variable, but early signs of the disorder include clumsiness, balance problems, and difficulty using the hands to grasp. Hearing loss occurs in some affected individuals, and eventually, some patients require the assistance of a wheelchair. Lifespan and intelligence are not typically affected.

Charcot-Marie-Tooth disease is comprised of several types and subtypes. CMT1 is responsible for almost half of all cases of CMT, with CMT2 and CMTX making up an additional 10-15% each. Within the CMT1 type, about 70-80% of cases are due to changes in the PMP22 most often associated with a duplication involving chromosome 17p12. Reciprocal deletions of this region are associated with hereditary neuropathy with liability to pressure palsies, HNPP.

Indications

Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutations within a family to allow for carrier testing and prenatal diagnosis.

Methodology

multiplex ligation-dependent probe amplification (MLPA)

Detection

An estimated 30-50% of patients diagnosed with Charcot-Marie-Tooth disease will have a copy number variant in the PMP22 gene. This analysis also detects deletions and duplications in the MPZ and GJB1 genes although sequence variants in these two genes are more common than copy number variants.

This test is available individually or as first-tier testing with reflex to the Charcot-Marie-Tooth Hereditary Neuropathy 54-gene panel.

Specimen Requirements

5 to 7 ml of peripheral blood collected in an EDTA (lavender top) tube is the preferred specimen type. The minimal blood needed for reliable DNA isolation is 3 ml. Extracted DNA, dried blood spots, and saliva are also accepted for this test.

Transport Instructions

The specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.

Prenatal Testing Information

Prenatal diagnosis is available if the familial mutations are known. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen.

Have Questions Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Kellie Walden, MS, CGC

MLPA, Molecular Testing
Meet Makayla Gunn

Meet Makayla Gunn

Makayla was diagnosed with Rett Syndrome in April of 2015 at the age of two.   At about 18 months, we noticed she had started some repetitive hand motions, and her pediatrician was a little concerned that she did not have many words.  She had learned some sign language, and was saying ‘mama’ and ‘dada’, but that was it.  Then she suddenly stopped all of that.  At her 2 year old check-up, the pediatrician referred us to BabyNet, ...

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