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Gilbert syndrome (UGT1A1 gene)

UGT1A1 · Pharmacogenomics · Evidence ★★★★☆

The UGT1A1 enzyme processes bilirubin, a yellow waste product. A common reduced version of the gene causes Gilbert syndrome, a harmless, mild jaundice when fasting or ill, and it also affects the HIV drug atazanavir.

Possible results

Typical bilirubin handling. You have the standard version of UGT1A1, the enzyme that processes bilirubin (a yellow waste product from old red blood cells). You clear bilirubin normally and aren't prone to the mild jaundice of Gilbert syndrome.

Mildly reduced bilirubin handling. You carry one reduced copy of UGT1A1, so you process bilirubin a little more slowly. This usually causes no symptoms, though it can tip into mild Gilbert-type jaundice when you're fasting or unwell. It can also matter for a few specific drugs like the HIV medication atazanavir.

Gilbert syndrome. You have two reduced copies of UGT1A1, which causes Gilbert syndrome: a common, harmless tendency for bilirubin to build up, sometimes giving a faint yellow tinge when you're fasting, stressed or sick. It needs no treatment, but it's worth knowing because it can increase side effects from a few drugs such as the HIV medication atazanavir.

Evidence & sources

Across global populations, about 14% of people carry two copies of this variant, and about 41% carry none.

CPIC provides dosing guidance for atazanavir based on this gene.

This variant appears in 34 published genetic studies: PubMed 19419973 · PubMed 21886157 · PubMed 22085899 · PubMed 22558097 · PubMed 23093944 · PubMed 23281178 · PubMed 23642732 · PubMed 24625756 · PubMed 24816252 · PubMed 25884002 · PubMed 26148204 · PubMed 27073872 · PubMed 31882771 · PubMed 33031748 · PubMed 34343768 · PubMed 34648354 · PubMed 34887591 · PubMed 35050183 · PubMed 35078996 · PubMed 35120996 · PubMed 35347128 · PubMed 35888748 · PubMed 35995766 · PubMed 36357675 · PubMed 36580335 · PubMed 36635386 · PubMed 37277652 · PubMed 38493369 · PubMed 38826804 · PubMed 38869630 · PubMed 39024449 · PubMed 39528826 · PubMed 39789286 · PubMed 42069741.

Related

CYP2C19 metabolizer status (clopidogrel & others) · Drug acetylation speed (NAT2) · Efavirenz / drug metabolism (CYP2B6*6) · Hepatitis C treatment response (IL28B) · Tacrolimus metabolism (CYP3A5 gene) · Thiopurine metabolism (TPMT and NUDT15 genes) · Warfarin dose sensitivity

References: dbSNP · GWAS Catalog · PubMed · CPIC guideline · SNPedia

Educational and informational only, not medical advice.

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