LMF1 Genotype (p.Ser319Arg)

This test looks at one very rare change in LMF1, short for lipase maturation factor 1. Your report lists it as c.957C>G, or p.Ser319Arg: one letter of the gene's code is swapped, so the 319th building block of the LMF1 protein becomes arginine instead of serine. The lab classifies it as a variant of uncertain significance (VUS), which means there is not yet enough evidence to say whether it affects your health.

That is an honest answer, not a hidden warning. No study of this change has been published, and no one has tested what it does to LMF1. Your triglyceride blood test, not this genotype, shows your actual level.

What LMF1 Does

Triglycerides in your blood are broken down mainly by an enzyme called lipoprotein lipase (LPL), with help from a related enzyme made in the liver, hepatic lipase. Both are made inside cells in an unfinished form. LMF1 is a helper protein, or chaperone, in the part of the cell that folds new proteins (the endoplasmic reticulum), and these lipases need it to mature into working enzymes. Without working LMF1, they are made but stay largely inactive.

When LMF1 Does Not Work

Researchers linked LMF1 to triglycerides in 2007. They traced a mouse condition called combined lipase deficiency to this gene, then found a person with two damaged copies of LMF1 who had the same pattern: low activity of both lipases and severe hypertriglyceridemia, meaning very high triglycerides.

LMF1 is now one of five genes in which two non-working copies can cause familial chylomicronemia syndrome (FCS). The others are LPL, APOC2, APOA5 and GPIHBP1. FCS is rare and recessive, meaning it needs a non-working copy from each parent. People with it have triglycerides persistently around 1,000 mg/dL or higher, usually from a young age, and a high lifetime risk of acute pancreatitis. LMF1 is one of the rarer causes.

One non-working copy is a different story. Reviews describe single rare changes in these five genes as adding to the risk of high triglycerides with variable effect: some carriers have raised levels and others do not, and other factors, including many common gene variants with small effects, play a large part. In one study of 563 people with severe hypertriglyceridemia, about 14 percent carried a single rare change in one of these genes, about 1 percent had two, and about 32 percent had a high load of common variants.

What Is Known About p.Ser319Arg

Very little. The change is extremely rare. In gnomAD v4, a reference database of more than 800,000 people, it appears on 7 of about 1.6 million gene copies, and no one in the database carries two copies. Your report's figure of about 0.000342 percent comes from the exome part of that database.

Computer prediction tools disagree about it. AlphaMissense, SIFT and PolyPhen-2 score it as likely harmful to the protein, but REVEL, a widely used tool that combines several other predictors, gives it a middling score that points neither way. Predictions are not measurements: the ACMG/AMP standards that labs use warn against overestimating computational evidence, and a prediction should not be the only evidence for classifying a variant. Under a 2025 calibration by ClinGen, an expert group that refines these standards, an AlphaMissense score this high can count as strong computer evidence, the most a prediction can earn. Under current ClinGen practice, computer evidence and rarity alone are generally not enough to call it likely pathogenic without more evidence, such as lab tests or patient data. No published study has reported this change in a patient or measured how LMF1 works with it, and ClinVar, the US public database of variant classifications, has no entry for it.

Experience with other LMF1 changes shows how hard these are to read. A 2012 study from an Amsterdam lipid clinic found eight LMF1 changes in people with severe hypertriglyceridemia. Several of them are fairly common in the general population, five also turned up in the study's control group, and the seven tested in the lab did not reduce lipase activity in the test used at the time. A French study of 385 patients found that some LMF1 changes did reduce lipase activity in the lab, including two of the Amsterdam ones. In 2026, a more sensitive lab test found that most of the Amsterdam changes modestly reduce LMF1 activity, leaving about 50 to 80 percent of normal, even though some of them are common in the general population and listed as benign in variant databases. Lab results, population frequency and triglyceride levels do not always line up, so until this specific change is studied directly, there is no way to say what it does.

What a VUS Means

Labs sort genetic variants into five groups: pathogenic, likely pathogenic, uncertain significance, likely benign and benign, following standards from the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP). Uncertain significance means the evidence is not strong enough either way. It is not a mild version of pathogenic, and the standards state that a VUS should not be used to make medical decisions. The aim instead is to resolve it as pathogenic or benign as more evidence comes in.

How Results Are Reported

Your report shows the two DNA letters at this position, one inherited from each parent, printed on the forward strand of chromosome 16. The usual letter is G and the variant letter is C. Papers and databases name the same change c.957C>G because LMF1 is read from the opposite strand, where each letter is swapped for its partner (G pairs with C). They are the same variant.

If your report also shows another rare change in LMF1, tell your clinician. Two different changes, one on each copy of the gene, can act like two copies of the same change, and these results alone cannot show whether the two changes sit on the same copy or on different ones; testing your parents can usually show which.

What this means for you: none of these results tells you your triglyceride level. Treat the genotype as context and the blood test as the answer.

The Blood Test Still Decides

A triglyceride blood test shows the level you actually have, and that number, not this genotype, is what guides care. If your triglycerides are in a healthy range, this variant is not causing high triglycerides right now. Levels can rise with weight gain, alcohol, poorly controlled diabetes, pregnancy, estrogen pills or some medicines, so keep checking them as part of routine care. If they are high, they deserve attention whatever your genotype, and a clinician may look at your other triglyceride genes and a polygenic score for the fuller picture.

Why You Only Need This Test Once

Your DNA does not change. Your result at this position at 25 will be the same at 65, so there is no reason to repeat this test over time (a one-time confirmation of a one- or two-copy result is different; see below). What can change is how the variant is classified, as researchers learn more about rare LMF1 changes.

What to Do With Your Result

Whatever your genotype, the next steps center on the blood test:

• Know your triglyceride level: if you have not had a recent triglyceride test, get one. It shows your actual level, which this genotype cannot.
• Do not read a VUS as a diagnosis: this result is not a diagnosis of any condition, and one copy has not been shown to raise triglycerides.
• Share it if your triglycerides are very high: if your level is very high, or you have had pancreatitis, show this result to your clinician so it can be read alongside your other triglyceride genes.
• Confirm before relying on it: some DNA tests can misread a change this rare. If you or your clinician want to use a one- or two-copy result, for example because your triglycerides are very high or another LMF1 change was also reported, ask for a clinical-grade genetic test to confirm it first.
• Expect it may be updated: a VUS can be reclassified as evidence builds, so it is worth asking about updates if your triglycerides are a concern.

For now, this result is a question mark, not a warning. Your triglyceride level is the number you can measure and act on.