Background:
Neuromuscular disorders are a group of heterogeneous conditions affecting the nervous system that controls muscle movements. This neuronal damage in turn causes degradation of the affected muscular tissue causing weakness and loss of muscle tone. Congenital muscular dystrophies have onsets ranging from birth to early infancy. Affected children may present with progressive muscle weakness, delayed motor development, joint contractures and spinal defects. This NGS tests for congenital muscular dystrophies including the following subtypes: defects of structural protein, defects of glycosylation, defects of proteins in endoplasmic reticulum, defects of nuclear envelope proteins, and dystroglycanopathies. Many of the congenital muscular dystrophies are autosomal recessive, however collagen VI deficient and LMNA-associated muscular dystrophies can be autosomal dominant.
Reasons for Referral:
- Abnormal serum creatine kinase levels
- Muscle degradation
- Abnormal electromyography (EMG)
- Abnormal nerve conduction studies (NCS)
- Positive family history (targeted testing is available if familial mutation is known).
- Carrier testing
Methodology:
This test has two components:
Component 1: Next generation sequencing will analyze the exons or coding regions of 20 Congenital Muscular Dystrophy-associated genes using Illumina NextSeq 500 technology and preparing samples using hybridization probes to enrich exonic regions. Promoter, intronic, etc. regions are not assessed here but may contain variants that impact gene function.
Component 2: A customized CytoSure “exon-centric” array (Oxford Gene Technology) will be used to detect deletions and duplications. The targeted array has enhanced probes targeted to the exonic regions of the of 20 Congenital Muscular Dystrophy-associated genes. The arrays will be run using Agilent SureScan technology. This array is an ideal complement to the next generation sequencing approach to provide a comprehensive mutation spectrum analysis for Congenital Muscular Dystrophy.
Congenital Muscular Dystrophy (20 genes): CHKB, COL6A1, COL6A2, COL6A3, DAG1, DPM1, DPM3, FKRP, FKTN, ISPD, ITGA7, LAMA2, LARGE, LMNA, POMGNT1, POMT1, POMT2, RYR1, SEPN1, TCAP
Specimen Requirements:
Blood: EDTA or ACD (Solution A or B):
- Adult: 5 mL
- Child: 5 mL
- Infant: 2-3 mL
DNA: 10µg at a minimum of 60-100ng/µL (DNA must be extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or CMS)
For routine testing of blood, saliva and buccal swabs, KDL does NOT accept samples from patients within two (2) weeks of a packed cell/platelet transfusion or within four (4) weeks of a whole blood transfusion. For extraordinary circumstances, where testing must be performed outside of the above windows, please contact our lab.
A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES. Please include detailed clinical information, including ethnicity, clinical history, and family history.
Test Performed (Days):
Weekly
Turn Around Time:
8 weeks
Shipment Sensitivity Requirements:
- Package and ship specimen to remain cold, but not frozen.
- Ship via overnight express, using the FedEx priority overnight label provided.
- Contact Client Services for shipping kits and instructions at (855) 535-1522.
References:
- GeneReviews: Congenital myopathies and congenital muscular dystrophies.
Curr Opin Neurol. 2001 Oct;14(5):575-82. http://www.ncbi.nlm.nih.gov/pubmed/11562568
- GeneReviews: Congenital Muscular Dystrophy Overview http://www.ncbi.nlm.nih.gov/books/NBK1291/
Additional Info: