Carrier screening or diagnostic testing for Joubert syndrome type 2 for individuals of Ashkenazi Jewish descent.
Polymerase Chain Reaction/Fluorescence Monitoring
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 1 mL)
Plasma or serum. Specimens collected in sodium heparin or lithium heparin tubes.
Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month
Background Information for Joubert Syndrome Type 2 (TMEM216), 1 Variant:
Characteristics: Joubert syndrome, type 2 is characterized by a "molar tooth sign" cerebellar and brain stem malformation, hypotonia and developmental delay. Clinical manifestations and severity of the syndrome vary.
Incidence: 1 in 34,000 in Ashkenazi Jewish individuals.
Inheritance: Autosomal recessive.
Cause: TMEM216 pathogenic variants.
Variants Tested: p.R73L (c.218G>T).
Clinical Sensitivity: 99 percent in Ashkenazi Jewish individuals; unknown in other ethnicities.
Methodology: Polymerase chain reaction (PCR) and fluorescence monitoring.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Variants other than p.R73L (c.218G>T) will not be detected. Diagnostic errors can occur due to rare sequence variations.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2013910||Joubert Syndrome Type 2, Specimen|
|2013911||Joubert Syndrome Type 2, Allele 1|
|2013912||Joubert Syndrome Type 2, Allele 2|
|2013913||Joubert Syndrome Type 2, Interp|