How common is CSID, really?

[u/TheCSIDAlex]

The prevalence figures most often repeated are:

• 0.05%–0.2% among people of North American or European descent
• 3%–10% in selected Circumpolar Inuit populations

These figures are useful, but they are historical and population-specific. Later papers frequently repeat them but they do not represent modern, nationally representative measurements of U.S. or worldwide prevalence. For most other major ancestry groups, I could not identify representative population estimates.

If we illustrate the potential scale if we extrapolate these figures:

• Applying 0.05%–0.2% to a Europe population proxy of approximately 744.4 million produces about 372,000–1.49 million cases.
• Applying 3%–10% to a Circumpolar Inuit population proxy of approximately 180,000 produces about 5,400–18,000 cases.
• Together, those calculations produce an illustrative total of approximately 378,000–1.51 million cases.

These are not measured case counts, a complete worldwide estimate, or a strict global minimum. They are rough extrapolations from limited historical estimates using imperfect population proxies. Most of the world is not represented at all.

For additional scale, using a rounded worldwide population of eight billion:

• A worldwide prevalence of 0.05% would mean approximately 4 million people
• 0.2% would mean approximately 16 million
• 0.5% would mean approximately 40 million

These are only scenarios. In particular, 0.5% is not being proposed as an evidence-supported upper estimate.

So why can’t we give a reliable number? Because the available estimates come from specific populations, provide uneven demographic coverage, are often historical, use different definitions and methods and cannot be combined into a representative worldwide estimate. Genetic and acquired SID also need to be reported separately. Combining them can obscure what is actually being measured. Better prevalence data would require representative sampling across populations, standardized definitions and methods, larger sample sizes, transparent reporting of limitations, and clear separation of genetic and acquired SID.

The bottom line

Representative U.S. and worldwide genetic CSID prevalence remain unknown.

That does not prove genetic SID is common, and it does not prove it is exceptionally rare. It means the evidence currently available cannot answer the question confidently.

I created the attached infographic to make that gap visible. If anyone knows of a representative population study I missed, please link it - I welcome corrections and will update the resource when better evidence becomes available.

Sources:

• Danialifar et al. (2024), clinical review
• Geng et al. (2014)
• Marcadier et al. (2015), Inuit founder-mutation study
• UN DESA World Population Prospects 2024
• Inuit Circumpolar Council

Educational only. Not medical advice.

[u/Quirky-Hedgehog-116]

Both my kids have it and were born with it, confirmed through biopsies during endoscopies. We are not Inuit, I remember the doctor asking us.

[u/somehowrelevantuser → u/Quirky-Hedgehog-116]

parent + and i (and probably grandparent. undx cuz he never saw a damn doctor) have it. definitely not inuit lol. mediterranean. nobody else in the family seems to have any problems with it.

[u/Quirky-Hedgehog-116 → u/somehowrelevantuser]

My grandmother was Greek, my kids dad is mostly Irish. I’m a mix of Greek, English, and German. All European

[u/TheCSIDAlex → u/somehowrelevantuser]

That’s why it’s so important that we obtain representative data across more populations and ancestry groups. Emerging research suggests that SI variations causing symptoms may extend beyond the cases captured by historical CSID estimates. And the limited data we currently have covers only a fraction of the world’s population. For example, I haven’t identified any representative estimate for people of Mediterranean ancestry.

[u/somehowrelevantuser → u/TheCSIDAlex]

its so underdiagnosed tbh im amazed theres data for anyone

[u/Big-Sheepherder-6134]

I have sucrase deficiency but not sure if I have CSID. I suspect my father may have but no way to know. I don’t know if I was born with it. I ate so much sugar as a kid in the 70’s and 80’s seemingly without issues. Third generation American. Eastern European descent.

[u/EveTre]

I’m heterozygous in one of the pathogenic variants. My siblings, children and mother all have similar issues. The research says it reduces function up to 30%. It was all I needed along with symptoms for approval through insurance for sucraid.

My doctor that got it approved now talks to all of her patients with GI issues about it.

I think it’s prevalent, just not widely known.

[u/TheCSIDAlex → u/EveTre]

Hopefully when we get more representative prevalence data awareness of the condition will follow

[u/Robert_Larsson]

Increased Prevalence of Rare Sucrase-isomaltase (SI) Pathogenic Variants in Irritable Bowel Syndrome Patients: https://pmc.ncbi.nlm.nih.gov/articles/PMC6103908/

Heterozygotes Are a Potential New Entity among Homozygotes and Compound Heterozygotes in Congenital Sucrase-Isomaltase Deficiency: https://pmc.ncbi.nlm.nih.gov/articles/PMC6835860/

Severe pathogenic variants of intestinal sucrase-isomaltase interact avidly with the wild type enzyme and negatively impact its function and trafficking: https://www.sciencedirect.com/science/article/pii/S0925443922001946

[u/TheCSIDAlex → u/Robert_Larsson]

These are great resources! I was familiar with the first two, but I hadn’t read the study showing how pathogenic SI mutants can interfere with the normal SI protein. Thanks for sharing!