Definition

The MECP2 gene encodes the MeCP2 protein, found in brain cells and critical for the development of synaptic connections between neurons. Pathogenic variants disrupt the protein's structure, leading to Rett syndrome, a progressive brain developmental disorder affecting language, communication, coordination and learning. More than 99% of cases are new (de novo) mutations with no family history; in the classic form, girls show normal development for 6 to 18 months before losing hand skills and undergoing regression.

Gene/region examined

MECP2 - Exon 2, MECP2 - Exon 3, MECP2 - Exon 4

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

X-linked dominant. Although a single altered copy is sufficient to cause the disease, cases occur almost exclusively in girls; in girls, who have two X chromosomes, X-inactivation provides partial compensation, while male infants with a single X chromosome are usually lost to severe neonatal encephalopathy.

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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