Confirm clinical diagnosis of TD type 1 or type 2.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Micromelia, macrocephaly, short ribs and a narrow thorax; TD I has bowed femurs and TD II has straight femurs and a cloverleaf skull; death usually occurs from respiratory insufficiency within hours or days of birth.
Incidence: 1 in 20,000 to 50,000 births.
Inheritance: Autosomal dominant; arising from a de novo mutation.
Cause: Fibroblast growth factor receptor 3 (FGFR3) gene mutations.
Mutations tested: c.742C>T (R248C), c.746C>G (S249C), c.1108G>T (G370C), c.1111A>T (S371C), c.1118A>G (Y373C), c.2419T>G (X807G), c.2419T>A (X807R), c.2420G>T (X807L), c.2420G>C (X807S), c.2421A>T (X807C), c.2421A>C (X807C) and c.2421A>G (X807W) for TD I and c.1948A>G (K650E) for TD II.
Clinical Sensitivity and Specificity: 99 percent.
Methodology: Polymerase chain reaction (PCR) and single nucleotide extension followed by capillary electrophoresis.
Analytic Specificity and Sensitivity: 99 percent.
Limitations: Mutations other than those targeted in FGFR3 will not be detected; analytic sensitivity may be compromised by rare primer site mutations. Diagnostic errors can occur due to rare sequence variations.
This test is performed pursuant to an agreement with Roche Molecular Systems, Inc.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|0051507||Thanatophoric Dysplasia I/II|
|2001382||Thanatophoric Dysplasia I/II Specimen|
- Fetal Thanatophoric dysplasia mutation assay
- FGFR3 mutation assay
- TD (Thanatophoric Dysplasia, Types 1 & 2 (FGFR3) 13 Mutations)