Definition

Biallelic pathogenic variants in the ADA gene disable the adenosine deaminase enzyme, which functions in purine metabolism; the toxic accumulation of deoxyadenosine metabolites within lymphocytes impairs the development of T, B and NK cells. A typical early-onset form diagnosed in infancy, ADA-SCID (~80%), and a milder late-onset form (ADA-CID, 15-20%) have been described; it accounts for approximately 15% of all SCID cases.

Gene/region examined

ADA - Exon 2, ADA - Exon 3, ADA - Exon 4, ADA - Exon 5, ADA - Exon 6, ADA - Exon 7, ADA - Exon 8, ADA - Exon 9, ADA - Exon 10

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Hereditary, autosomal recessive (AR).

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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