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Benign Hereditary Chorea Test

Genes:
NKX2-1

Syndrome Information

Clinical Description

Benign Hereditary Chorea (BHC) is an autosomal dominant condition in which patients experience early onset (by 5 years), non-progressive or slowly progressive chorea. Dysarthria and gait abnormalities are also reported.  Unlike patients with Huntington Disease, BHC patients do not develop dementia.  Intelligence is normal to slightly below normal.  BHC is heterogeneous, and not all families have been linked to chromosome 14 or the NKX2-1 gene.

Inheritance Pattern

Autosomal Dominant

Genotype-Phenotype Correlation

None known

Test Information

Test Method

Bidirectional sequencing of the coding regions and intron-exon boundaries of NKX2-1;Multiplex ligation-dependent probe amplification (MLPA) for gene deletions

Clinical Utility

Identification of causative mutations in known or highly suspicious cases of BHC; rule-out inherited causes of chorea; diagnostic or presymptomatic testing of at-risk relatives of a proband;  predictive prenatal testing when familial mutation is known. 

Clinical Sensitivity

We were not able to locate any published series of patients with BHC who were evaluated for NKX2-1 mutations.  Of reported mutations, 9 are point mutations and 1 is a gene deletion.  Our combined sequencing and MLPA assay should detect all reported mutations. In a series of families undergoing linkage analysis, 3 of 7 families showed linkage to chromosome 14

Analytic Sensitivity

Sequencing:  Greater than 97% for nucleotides analyzed.  All reports will indicate if a certain percentage of nucleotides were not called or were analyzed in a single direction.

MLPA:  Analytical sensitivity for deletions is estimated to be at least 90% 

Sample Requirements

3-6ml whole blood in EDTA (purple topped) tubes. (see Pediatric or Adult blood sample algorithms for additional information)

We prefer whole blood for all tests. For tests utilizing MLPA, we are only able to accept whole blood drawn in EDTA (purple or lavender top) tubes and Qiagen Puregene extracted DNA.

Turn Around Time

Sequencing: 2-3 weeks
MLPA: up to 4 weeks

Fee and CPT Codes

Sequencing:  $882 for routine testing on a blood or DNA sample
CPT Code: 81479

MLPA: $429 for routine testing on a blood or DNA sample
CPT Cpde:  81479

Please contact the lab to arrange testing for known mutations on blood or prenatal samples. 

Special Considerations

This test is offered as an automatic reflex to MLPA analysis if the sequencing assay does not detect a potential disease-causing mutation. NKX2-1 mutations are also associated with Choreoathetosis, Hypothyroidism, and Neonatal Respiratory Distress Syndrome (also known as Brain Lung Thyroid Syndrome).


INFORMED CONSENT from the patient is required prior to ordering a genetic test. The DNA Diagnostic Lab's consent is located on the second page of the requisition form. There is also a patient brochure, "Things Every Patient Should Know Before Consenting to a Genetic Test", available for download.