Ordering Recommendation

Confirm clinical diagnosis of thanatophoric dysplasia type 1 or type 2.

Mnemonic
TD PAN
Methodology

Polymerase Chain Reaction/Fragment Analysis

Performed

Sun-Sat

Reported

3-7 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).

Specimen Preparation

Transport 3 mL whole blood. (Min: 1 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions
Remarks
Stability

Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable

Reference Interval
Interpretive Data

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.

Compliance Category

Laboratory Developed Test (LDT)

Note
Hotline History
N/A
CPT Codes

81479

Components
Component Test Code* Component Chart Name LOINC
0051507 Thanatophoric Dysplasia I/II 75391-3
2001382 Thanatophoric Dysplasia I/II Specimen
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Aliases
  • Fetal Thanatophoric dysplasia mutation assay
  • FGFR3 mutation assay
  • TD
Thanatophoric Dysplasia, Types 1 and 2 (FGFR3) 13 Mutations