Definition

Achondroplasia is the most common cause of disproportionate short stature; it presents with shortened limbs, an enlarged head and characteristic facial features. Hypochondroplasia is a similar but milder form. Both result from gain-of-function mutations in the FGFR3 gene that keep the receptor constantly active and excessively suppress chondrocyte proliferation; FGFR3 variants form a severity spectrum running from hypochondroplasia to achondroplasia to SADDAN to thanatophoric dysplasia.

Gene/region analyzed

FGFR3 - Exon 9, FGFR3 - Exon 10, FGFR3 - Exon 13, FGFR3 - Exon 15

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Inherited in an autosomal dominant manner; about 80% of cases result from a de novo mutation and 20% are inherited from an affected parent. An affected individual has a 50% risk of passing it on to each child.

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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