CSID is considered to be a rare, autosomal recessive disorder, and because its symptoms overlap with more common gastrointestinal disorders, it is often difficult to diagnose. It is likely that the true prevalence of CSID is underestimated, and that numerous patients suffering from chronic diarrhea and/or abdominal pain may in fact have CSID, but remain undiagnosed. Many patients with CSID may wait numerous years for a diagnosis because the incidence is so rare and because the currently accepted diagnostic tools are invasive procedures. Recent clinical studies and recent genetic studies suggest that CSID is a more common disease than previously thought.
Past clinical studies of smaller population groups showed high rates of CSID (5-10% in Greenland Eskimos, 3-7% in Canadian native peoples, 3% in Alaskans of native ancestry). Estimates of the prevalence of CSID in other North American and European populations are lower at 1 in 500 to 1 in 2000 among non-Hispanic Caucasians, which would equal approximately 0.2%. The rates are even lower in African-Americans and Caucasians of Hispanic descent. The prevalence for those people with a level of sucrase activity below the lower limit for the normal population was estimated in one study to be 8.9% in the United States population.
In a recent genetic study (Uhrich S, Wu Z, Huang J, et al., 2012), four mutations that cause CSID were identified and emerged as the most common mutations. These four mutations are present in 0.5% of normal controls. This means that there could be up to approximately 1,000,000 carriers of CSID in the United States, which represents approximately 4% of the general population in the United States. Additional studies are underway and could help with more accurately determining the prevalence of CSID. It is possible that a significant proportion of affected pediatric and adult patients are not being tested, and therefore not being diagnosed with CSID. CSID occurs equally as frequently in males and females.