Congenital Myasthenic Syndrome with Episodic Apnea via the CHAT Gene
Summary and Pricing 
Test Method
Sequencing and CNV Detection via NextGen Sequencing using PG-Select Capture Probes| Test Code | Test Copy Genes | Test CPT Code | Gene CPT Codes Copy CPT Code | Base Price | |
|---|---|---|---|---|---|
| 7003 | CHAT | 81479 | 81479,81479 | $990 | Order Options and Pricing |
Pricing Comments
Testing run on PG-select capture probes includes CNV analysis for the gene(s) on the panel but does not permit the optional add on of exome-wide CNV analysis. Any of the NGS platforms allow reflex to other clinically relevant genes, up to whole exome or whole genome sequencing depending upon the base platform selected for the initial test.
An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.
This test is also offered via a custom panel (click here) on our exome or genome backbone which permits the optional add on of exome-wide CNV or genome-wide SV analysis.
Turnaround Time
3 weeks on average for standard orders or 2 weeks on average for STAT orders.
Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.
Targeted Testing
For ordering sequencing of targeted known variants, go to our Targeted Variants page.
Clinical Features and Genetics
Clinical Features
Congenital myasthenic syndromes (CMS) are disorders of the neuromuscular junction resulting from abnormalities of presynaptic, synaptic, or postsynaptic proteins. CMS are characterized by fatigable weakness affecting limb, ocular, facial, and bulbar muscles. Neonates present with feeding problems, choking, feeble cry, and muscle weakness. Patients presenting in later childhood are seen with abnormal exercise-induced fatigue and difficulty running. Most patients present prior to 2 years of age although rare exceptions are reported (eg. Croxen et al. Neurol 59:162-168, 2002). Symptoms are extremely variable and are in some cases induced by febrile illness, infection, or excitement (eg. Byring et al. Neuromuscul Disord 12:548-553, 2002). Life-threatening respiratory crises may occur in affected neonates or older children. CMS may be differentiated from myasthenia gravis, an acquired autoimmune disorder, by earlier age at onset and by negative serology tests for anti-acetylcholine receptor (AchR) and anti-Musk antibodies. CMS with choline acetyltransferase variants can be differentiated from other forms of CMS clinically by the occurrence of apnea, and pathophysiologically by its effects at the presynaptic membrane.
Genetics
Abnormalities of proteins involved with neuromuscular transmission underlie CMS, limb girdle CMS, Pena-Shokeir syndrome, and multiple pterygium syndromes. These disorders, which may represent a phenotypic continuum of a single entity, are most often inherited in an autosomal recessive manner. Presynaptic CMS with episodic apnea (OMIM 254210) is inherited as an autosomal recessive condition secondary to variants in CHAT (OMIM 118490). Variants result in null alleles or reduced CHAT expression (Ohno et al. Proc Natl Acad Sci USA 98:2017-2022, 2001), or affect the substrate binding or catalytic sites of the enzyme (Cai et al. EMBO J 23:2047-2058, 2004).
Choline acetyltransferase is encoded by exons 1 – 15 of the CHAT gene located on chr 10q11.
Clinical Sensitivity - Sequencing with CNV PG-Select
Sensitivity for CMS testing is at least 50% overall; 30% for CHRNE, 10% for RAPSN, and 7.5% for COLQ (GeneReviews, Abicht and Lochmüller, 2006). Clinical sensitivity should be high for cases with episodic apnea.
Testing Strategy
This test provides full coverage of all coding exons of the CHAT gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.
Indications for Test
A comprehensive diagnostic algorithm can be found in (GeneReviews, Abicht and Lochmüller, 2006). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in CHAT.
A comprehensive diagnostic algorithm can be found in (GeneReviews, Abicht and Lochmüller, 2006). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in CHAT.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| CHAT | 118490 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Disease
| Name | Inheritance | OMIM ID |
|---|---|---|
| Familial Infantile Myasthenia | AR | 254210 |
Citations
- Angela Abicht, Hanns Lochmuller (2006). "Congenital Myasthenic Syndromes."
- Byring RF, Pihko H, Tsujino A, Shen XM, Gustafsson B, Hackman P, Ohno K, Engel AG, Udd B. 2002. Congenital myasthenic syndrome associated with episodic apnea and sudden infant death. Neuromuscul Disord 12: 548-553. PubMed ID: 12117478
- Cai, H., et.al. (2008). "ALS2/alsin knockout mice and motor neuron diseases." Neurodegener Dis 5(6): 359-66. PubMed ID: 18714162
- Croxen R, Hatton C, Shelley C, Brydson M, Chauplannaz G, Oosterhuis H, Vincent A, Newsom-Davis J, Colquhoun D, Beeson D. 2002. Recessive inheritance and variable penetrance of slow-channel congenital myasthenic syndromes. Neurology 59: 162-168. PubMed ID: 12141316
- Ohno, K., et.al. (2001). "Choline acetyltransferase mutations cause myasthenic syndrome associated with episodic apnea in humans." Proc Natl Acad Sci U S A 98(4): 2017-22. PubMed ID: 11172068
Ordering/Specimens
Ordering Options
We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.
myPrevent - Online Ordering
- The test can be added to your online orders in the Summary and Pricing section.
- Once the test has been added log in to myPrevent to fill out an online requisition form.
- PGnome sequencing panels can be ordered via the myPrevent portal only at this time.
Requisition Form
- A completed requisition form must accompany all specimens.
- Billing information along with specimen and shipping instructions are within the requisition form.
- All testing must be ordered by a qualified healthcare provider.
For Requisition Forms, visit our Forms page
If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.
Specimen Types
Specimen Requirements and Shipping Details
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ORDER OPTIONS
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