Test Directory

Clear All
Test Code
1483
Test Name
Short-rib Or Thoracic Dysplasia 4 With Without Polydactyly
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
SRTD4
Description

Short-rib thoracic dysplasia 2 with or without polydactyly (SRTD2; MIM 611263), SRTD3 (MIM 613091), SRTD4 (MIM 613819), SRTD5 (MIM 614376), SRTD6 (MIM 263520), SRTD7 (MIM 614091) and SRTD8 (MIM 615503) display similar clinical, radiological and histological features.  All of these disorders are ciliopathies characterized by short ribs with a narrow thorax, short long bones and a trident appearance of the acetabular roof with or without polydactyly.  Extra skeletal findings may include anomalies of the brain, eye, genitalia, heart, intestines, kidney, liver, and pancreas. SRTDs are among the most common autosomal recessive osteochondrodysplasias.

SRTD2 is caused by mutations in the IFT80 gene, which codes for intraflagellar transport protein 80 homolog.  IFT80 is a component of the intraflagellar transport complex B, which is essential for the development and maintenance of motile and sensory cilia.  

SRTD3 is caused by mutations in the cytoplasmic dynein 2 heavy chain 1 gene (DYNC2H1), which codes for a component of the cytoplasmic dynein complex.  Specifically, it codes for the %u201Cmotor%u201D responsible for retrograde intraflagellar transport from the cilia tip to basal body.

SRTD4 is caused by mutations in the tetratricopeptide repeat protein 21B gene (TTC21B).  This gene encodes an axonemal protein required for the retrograde intraflagellar transport. 

SRTD5 is caused by mutations in the WDR19 gene, which codes for WD repeat-containing protein 19.  It is involved in retrograde ciliary transport. 

SRTD6 is caused by mutations in the NEK1 gene.  A digenic diallelic mode of inheritance has also been proposed because of the identification of heterozygous mutations in the NEK1 and DYNC2H1 genes. NEK1 encodes serine/threonine-protein kinase Nek1 with numerous proposed roles. It seems to have a critical role in cell-cycle associated ciliogenesis, DNA double strand repair and neuronal development.

SRTD7 is caused by mutations in the WDR35 gene, which encodes WD repeat-containing protein 35.  Mutations result in the abrogation or interruption of retrograde transport.

SRTD8 is caused by mutations in the WDR60 gene, which codes for the WD repeat-containing protein 60. The function of WDR60 is poorly characterized but fibroblast derived from an affected individual displayed a defect in ciliogenesis.
Testing Schedule
Monday-Friday
Genes
TTC21B
MIM
613819
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.
© 2026 HNL Lab Medicine. All rights reserved.