Confirm clinical diagnosis of thanatophoric dysplasia type 1 or type 2.
Polymerase Chain Reaction/Fragment Analysis
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 1 mL)
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Background information for Thanatophoric Dysplasia, Types I and II (FGFR3) 13 Mutations
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.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|0051507||Thanatophoric Dysplasia I/II||75391-3|
|2001382||Thanatophoric Dysplasia I/II Specimen|
- Fetal Thanatophoric dysplasia mutation assay
- FGFR3 mutation assay