Definition

This is the most common lethal skeletal dysplasia, usually fatal in the perinatal period. There are two types: Type 1 presents with curved femurs, with about 90 percent of cases caused by the p.Arg248Cys and p.Tyr373Cys variants; Type 2 presents with straight femurs and a cloverleaf skull deformity, with a single variant (p.Lys650Glu) found in all cases. Both types result from ligand-independent, gain-of-function activation of FGFR3; most infants die in the perinatal period from respiratory failure due to a narrow chest.

Gene/region examined

FGFR3 - Exon 10, Exon 15

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Inherited in an autosomal dominant manner; in the large majority of cases the FGFR3 variant is de novo.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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