Gaucher disease type 1 (carrier)

The GBA gene makes an enzyme that recycles fatty molecules inside cells. The most common Gaucher variant is the leading cause of Gaucher disease type 1, and one copy makes you a carrier.

What this GBA1 variant does

GBA1 makes glucocerebrosidase, the lysosomal enzyme that breaks down a fatty molecule called glucocerebroside. This variant, known as N370S or N409S depending on the numbering convention, leaves partial enzyme activity, which is why it is associated with the mildest form of Gaucher disease rather than the severe neurological ones.

Carrying one copy does not cause Gaucher disease. Two copies, or one alongside another damaging GBA1 variant, can produce type 1 Gaucher disease, where the undegraded material accumulates in the spleen, liver and bone marrow.

How strong the evidence is

This is a well-characterised pathogenic variant rather than a statistical association. ClinVar records it with 50 submitters under Gaucher disease type I, and also under late-onset Parkinson disease and Lewy body dementia.

The carrier frequency is what makes it worth reading: in the Ashkenazi Jewish population, GBA1 carrier frequency is roughly 1 in 12 to 1 in 16, and this variant accounts for around 70% of the carried alleles. In the 1000 Genomes reference data it is much rarer elsewhere, at around 0.35% of European-ancestry individuals and essentially absent in East Asian samples.

The Parkinson's association, stated carefully

GBA1 variants are among the most common genetic risk factors for Parkinson's disease, and this one is included. A multicentre analysis found people with Parkinson's had substantially higher odds of carrying a Gaucher-associated variant than controls, with reported odds ratios in the range of five to seven.

Two things keep that in proportion. A raised relative risk on a condition that affects roughly 1% to 2% of people over 60 still leaves the great majority of carriers unaffected, and there is currently no treatment or screening protocol that a carrier result changes. Some people want to know this and some do not, which is a reasonable thing to decide before reading further.

Why carrier status matters for family planning

Gaucher disease type 1 is recessive, so it appears when a child inherits a damaging GBA1 variant from both parents. Two carriers have a one in four chance in each pregnancy. This is the situation where a carrier result is concretely useful, and it is a standard reason to see a genetic counsellor, particularly for couples with Ashkenazi Jewish ancestry, where carrier screening panels routinely include GBA1.

What this variant does not tell you

Hundreds of GBA1 variants are known and this file reads one. A negative result here does not rule out carrier status for another GBA1 variant, and consumer genotyping chips cannot sequence the gene, which is additionally complicated by a nearby pseudogene that standard methods can confuse.

It also says nothing about severity. Type 1 Gaucher disease ranges from lifelong silence to significant enlargement of the spleen and liver, bone disease and low blood counts, and it is now treatable with enzyme replacement and substrate reduction therapy.

What each rs76763715 genotype means

rs76763715 has three possible genotypes: TT, CT and CC.

No Gaucher variant (rs76763715 TT). You don't carry the most common Gaucher variant, the leading cause of Gaucher disease (an inherited condition where fatty molecules build up in cells). From what this variant shows you're not a carrier.

Gaucher carrier (rs76763715 CT). You carry one copy of the most common Gaucher variant, which makes you a carrier. Carriers are typically healthy, but if a partner is also a carrier, a child could inherit two copies, so it can be useful to know for family planning. This variant is also a mild Parkinson's risk factor, separate from carrier status.

Two Gaucher variants (rs76763715 CC). You have two copies of the most common Gaucher variant. This is the most common form of Gaucher disease and is often mild or even without symptoms, but it's worth discussing with a doctor, since the condition is manageable and treatments exist.

Evidence & sources

Across global populations, fewer than 1% of people carry two copies of this variant, and about 100% carry none.

Common questions

Does being a Gaucher carrier make me ill? Carriers of one copy do not develop Gaucher disease. The one association worth knowing is a raised, still modest, risk of Parkinson's disease and Lewy body dementia, which no current intervention acts on.

Should my partner be tested? If you are planning a pregnancy and either of you has Ashkenazi Jewish ancestry, carrier screening for both partners is the standard approach, and it covers far more genes than a consumer file reads. A genetic counsellor is the right route rather than comparing two consumer results.

Related

Alpha-1 antitrypsin deficiency · G6PD deficiency (favism) · Hereditary hemochromatosis (HFE gene)