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Test Code
1759
Test Name
Thanatophoric I Dysplasia, Type / II
CPT Codes
81479
Expected Turnaround Time
Typically 2 to 4 weeks from receipt of a sample in the laboratory. All cases involving ongoing pregnancies will be expedited.
Clinical Utility
Genetic analysis to provide a molecular diagnosis of this disorder. Recommended for individuals with a personal and/or family history of this disorder to ensure appropriate treatment and establish recurrence risk for family members.
Specimen and Container Info

Non-Prenatal Specimens

Preferred/Alternate

Specimen Type

Containers

Volume

Preferred Specimen Type

Whole Blood

Lavender Top (EDTA)

3 mL

Alternate Specimen Type

Genomic DNA

1.5 mL Tube

3 µg (at a concentration of at least 30 ng/µl), preferably in TE solution.

Alternate Specimen Type

Fibroblasts

T-25 Flasks

2 confluent T-25 flasks, filled to capacity

Alternate Specimen Type

Saliva (Whole blood is recommended for CNV)

DNA Self-Collection Kit or Oragene Saliva Collection Kit for Young Children

Follow kit instructions (www.dnagenotek.com)

Prenatal Specimens

Either specimen type below is acceptable.

Specimen Type

Containers

Volume

Cultured cells

T-25 Flasks

2 confluent T-25 flasks derived from amnio or CVS samples.

Genomic DNA

1.5 mL Tube

3 µg (at a concentration of at least 30 ng/µl), preferably in TE solution.

NOTE: For specimens from outside of North America, the preferred specimen type is Genomic DNA. HNL Genomics does not recommend shipping whole blood or cultured cells from any location other than the United States, Canada, or Mexico.
Transport Instructions
  • Transport at room temperature within 24 hours.
  • If the specimen cannot be transported to the lab within 24 hours, refrigerate for up to 72 hours.
  • Do not freeze or expose to extreme temperatures, refrigerate for up to 72 hours if cannot be transported to lab within 24 hours. 
Stability Requirements

Room Temperature

24 hours

Refrigerated

72 hours
Causes for Rejection
  • Improperly labeled specimen (minimum of two patient identifiers)
  • Inappropriate specimen type
  • Incomplete or incorrect test request form
  • Insufficient volume
  • Specimen has leaked in transit
  • Specimen without a test order
Methodology
Next Generation Sequencing and Copy Number Variation Analysis
Performing Location
Genomics - Snowdrift
Alternate Names
TD1; TD2
Description

Achondroplasia (ACH; MIM 100800) and hypochondroplasia (HCH; MIM 146000) are autosomal dominant disorders. ACH is caused by specific mutations in FGFR3. ACH represents the most common skeletal dysplasia in humans. It is characterized by rhizomelic dwarfism, trident hands and short fingers, midface hypoplasia with macrocephaly and frontal bossing. A small foramen magnum may cause generalized hypotonia, hyperreflexia or clonus in newborns. HCH is similar to but milder than ACH. Patients are still rhizomelic dwarfs but are not as short, do not have trident hands and the facial manifestations are not as severe. Neurological complications in HCH are not constant findings. HCH is genetically heterogeneous. Not all patients diagnosed clinically with HCH have demonstrable mutations in FGFR3.

Severe achondroplasia with developmental delay and acanthosis nigricans

Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) is an autosomal dominant disorder caused by a specific mutation in FGFR3. These patients have profound short stature, midface hypoplasia, developmental delay, mental retardation and develop acanthosis nigricans. These patients share the FGFR3 mutation also responsible for thanatophoric dysplasia II.

Thanatophoric dysplasia, type I and II

Thanatophoric dysplasia, type I (TD1; MIM 187600) and thanatophoric dysplasia, type II (TD2; MIM 187601) are autosomal dominant disorders caused by mutations in FGFR3. TD is the most common neonatal lethal skeletal dysplasia. Infants are severe rhizomelic dwarfs, have midface hypoplasia and a very small foramen magnum. The ribs are short resulting in a small thorax and respiratory compromise. Types I and II are recognized and correlated with specific FGFR3 mutations. Type I is associated with curved tubular bones and has several different FGFR3 mutations. Type II has a cloverleaf skull and straight femurs and has a specific FGFR3 mutation.
Testing Schedule
Monday-Friday
Genes
FGFR3
MIM
187600, 187601
Disease Group
Skeletal Disorders
The American Medical Association (AMA) Current Procedural Terminology (CPT) codes published by HNL Lab Medicine are guidelines and are intended for informational purposes only. CPT coding is the exclusive responsibility of the billing entity. View the Terms.
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