Definition

A microdeletion spanning the imprinted SNRPN/PWS-IC region in 15q11.2-q13; a deletion on the paternally inherited chromosome leads to Prader-Willi syndrome (infantile hypotonia, followed by hyperphagia and obesity), while a deletion on the maternally inherited chromosome leads to Angelman syndrome (severe intellectual disability, absence of speech, epilepsy); in both syndromes, approximately 70% of cases result from this regional deletion.

Method

FISH analysis

Accepted sample types

Amniotic fluid, Chorionic villus, Cord blood

Inheritance

Usually de novo; when parentally inherited, the recurrence risk varies according to the imprinting pattern.

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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