DWARFISM PANEL (FGFR 3)
Tests performed in the Panel: Achondroplasia (ACH) and Hypochondroplasia (HCH)
Gene Symbol: FGFR3; see individual test pages for additional information.
TURNAROUND TIME: 10 days
TESTING METHODOLOGY: Polymerase chain reaction (PCR) and DNA Sequencing of the region of exon 10 encompassing the most common HCH mutations. Detection of a G380R (c.1138G>A or G>C) mutation by PCR and restriction enzyme digestion.
- Collect: Prefer two 5ml whole blood EDTA (lavender top) tube.
- Min. Collection: 0.7 ml whole blood EDTA.
- Transport: blood EDTA at Room Temp shipped regular next day air (No Saturday delivery; store specimen at 4°C and ship Monday).
- Stability: Ambient: up to 7 days; Refrigerated: 2 weeks. Frozen: unacceptable
- Unacceptable Conditions: Serum. Frozen or severely hemolyzed blood. Clotted blood.
- Prenatal testing: Direct: 5ml direct unspun amniotic fluid or 15mg CVS tissue with a backup flask growing. Culture: confluent T25 flask. Maternal blood sample is required for maternal cell contamination studies.
Counseling and informed consent are recommended for genetic testing. A consent form
is available as a resource but not required.
Incidence: unknown; estimated to be 1 in 15,000 - 40, 000.
Inheritance: may be spontaneous or inherited in an autosomal dominant manner
Disease Characteristics: Both syndromes are characterized by abnormal bone growth that results in short stature with disproportionately short arms and legs, & macrocephaly. Other symptoms may include hypotonia in infancy; broad, short hands and feet; or mild joint laxity depending on the diagnosis. In both, intelligence and life span are usually normal.
Clinical Sensitivity: please see individual test pages
Test Limitations: Mutations lying outside the tested regions (roughly 5-10% of cases of hypochondroplasia) will not be detected. Rare diagnostic errors can occur due to primer / probe site mutations or rare polymorphisms.
INDICATIONS FOR USE:
- To confirm the nature of the dwarfism in an affected individual.
- To evaluate fetuses with abnormal ultrasound findings for the possibility of spontaneous ACH
- To evaluate Individuals at risk who wish prenatal diagnosis.