Strong Genetic

Canavan Disease

Name: Canavan Disease
Creator: Realised
Published: 2026-03-01

GeneASPArsIDrs28940279, rs28940893, rs121434536InheritanceAutosomal recessiveCarrier frequency~1 in 40 Ashkenazi Jewish, ~1 in 200+ general EuropeanSystemCarrier Screening

Summary

Canavan disease is a progressive neurological condition caused by deficiency of the enzyme aspartoacylase, which breaks down N-acetylaspartic acid (NAA) in the brain. When NAA accumulates, it causes spongy degeneration of the brain's white matter — the insulating myelin sheaths that allow nerve signals to travel efficiently are destroyed.

Practical takeaway

This matters when planning children, particularly if your partner is also of Ashkenazi Jewish descent — where carrier frequency is approximately 1 in 40. A carrier test through a GP or genetic counselling service can determine your partner's status. If you are both carriers, a genetic counsellor can discuss prenatal testing options and what Canavan disease means in practice. This conversation is best had before pregnancy, allowing time for informed decision-making. Realised does not calculate reproductive risk or advise on reproductive decisions.

Evidence detail

What Carrier Status Means For You

You are not affected. One working copy of ASPA produces enough aspartoacylase for normal brain development and function. Your carrier status becomes relevant if your partner also carries an ASPA variant. In that case, each child has a 25% chance of having Canavan disease, a 50% chance of being an unaffected carrier, and a 25% chance of inheriting neither variant.

Population Context

Canavan disease carrier frequency is dramatically higher in the Ashkenazi Jewish population (~1 in 40) than in the general European population (~1 in 200 or lower). The E285A variant accounts for approximately 98% of Ashkenazi alleles and likely spread through a founder effect in the Ashkenazi population. The A305E variant is the most common pathogenic variant in non-Jewish Europeans. Canavan disease is part of the standard Ashkenazi Jewish carrier panel recommended by ACMG and ACOG, and carrier screening has significantly reduced the birth incidence in screened populations.

Limitations

23andMe tests 3 of over 70 known pathogenic ASPA variants. For Ashkenazi Jewish individuals, coverage is high — E285A and Y231X capture the vast majority of disease alleles. For non-Ashkenazi individuals, coverage is lower because the A305E variant, while common in Europeans, does not account for as large a proportion of alleles. A "not detected" result reduces but does not eliminate carrier risk. Comprehensive carrier screening through a clinical laboratory covers more variants, especially for individuals of non-Ashkenazi ancestry.

Sources (5)

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