Current research suggests that nearly 8% of the population has at least partial DPD deficiency. A diagnostics determination test for DPD deficiency is available and it is expected that with a potential 500,000 people in North America using 5-FU this form of testing will increase. The whole genetic events affecting the DPYD gene and possibly impacting on its function are far from being elucidated, and epigenetic regulations could probably play a major role in DPD deficiency. It seems that the actual incidence of DPD deficiency remains to be understood because it could depend on the very technique used to detect it. Screening for genetic polymorphisms affecting the "DPYD" gene usually identify less than 5% of patients bearing critical mutations, whereas functional studies suggest that up to 20% of patients could actually show various levels of DPD deficiency.

Women could be more at risk than men. It is more common among African-Americans than it is among Caucasians.

This condition is very rare; approximately 600 cases have been reported worldwide. In most parts of the world, only 1% to 2% of all infants with high phenylalanine levels have this disorder. In Taiwan, about 30% of newborns with elevated levels of phenylalanine have a deficiency of THB.

PNP-deficiency is extremely rare. Only 33 patients with the disorder in the United States have been documented. In the United Kingdom only one child has been diagnosed with this disorder.

Vitamin E deficiency is rare and is almost never caused by a poor diet. Instead, there are three specific situations when a vitamin E deficiency is likely to occur:

- Premature, very low birth weight infants - birth weights less than 1500 grams, or 3.5 pounds. A neonatologist, a pediatrician specializing in the care of newborns, typically evaluates the nutritional needs of premature infants.

- Rare disorders of fat metabolism - There is a rare genetic condition termed isolated vitamin E deficiency or 'ataxia with isolated with vitamin E deficiency', caused by mutations in the gene for the tocopherol transfer protein. These individuals have an extremely poor capacity to absorb vitamin E and develop neurological complications that are reversed by high doses of vitamin E.

- Fat malabsorption - Some dietary fat is needed for the absorption of vitamin E from the gastrointestinal tract. Anyone diagnosed with cystic fibrosis, individuals who have had part or all of their stomach removed or who have had a gastric bypass, and individuals with malabsorptive problems such as Crohn's disease, liver disease or exocrine pancreatic insufficiency may not absorb fat (people who cannot absorb fat often pass greasy stools or have chronic diarrhea and bloating). Abetalipoproteinemia is a rare inherited disorder of fat metabolism that results in poor absorption of dietary fat and vitamin E. The vitamin E deficiency associated with this disease causes problems such as poor transmission of nerve impulses, muscle weakness, and degeneration of the retina that can cause blindness.

Prevalence varies by population, but is on the order of 1 in 100 to 1 in 1000 people, making it relatively common for a genetic disease.

SigAD occurs in 1 of 39 to 57 patients with celiac disease. This is much higher than the prevalence of selective IgA deficiency in the general population. It is also significantly more common in those with type 1 diabetes.

It is more common in males than in females.

Prognosis is excellent, although there is an association with autoimmune disease. Of note, selective IgA deficiency can complicate the diagnosis of one such condition, celiac disease, as the deficiency masks the high levels of certain IgA antibodies usually seen in celiac disease.

As opposed to the related condition CVID, selective IgA deficiency is not associated with an increased risk of cancer.

Patients with Selective IgA deficiency are at risk of anaphylaxis from blood transfusions. These patients should receive IgA free containing blood products and ideally blood from IgA-deficient donors.

C2 deficiency has a prevalence of 1 in about 20,000 people in Western countries.

Some situations that increase the need for folate include the following:

- hemorrhage

- kidney dialysis

- liver disease

- malabsorption, including celiac disease and fructose malabsorption

- pregnancy and lactation (breastfeeding)

- tobacco smoking

- alcohol consumption

The cause of complement deficiency is genetics (though cases of an acquired nature do exist post infection). The majority of complement deficiencies are autosomal recessive, while properdin deficiency could be X-linked inheritance, and finally MBL deficiency can be both.

Heterozygous protein C deficiency occurs in 0.14–0.50% of the general population. Based on an estimated carrier rate of 0.2%, a homozygous or compound heterozygous protein C deficiency incidence of 1 per 4 million births could be predicted, although far fewer living patients have been identified. This low prevalence of patients with severe genetic protein C deficiency may be explained by excessive fetal demise, early postnatal deaths before diagnosis, heterogeneity in the cause of low concentrations of protein C among healthy individuals and under-reporting.

The incidence of protein C deficiency in individuals who present with clinical symptoms has been reported to be estimated at 1 in 20,000.

In the US, the Dietary Reference Intake for adults is 55 µg/day. In the UK it is 75 µg/day for adult males and 60 µg/day for adult females. 55 µg/day recommendation is based on full expression of plasma glutathione peroxidase. Selenoprotein P is a better indicator of selenium nutritional status, and full expression of it would require more than 66 µg/day.

Based on the results of worldwide screening of biotinidase deficiency in 1991, the incidence of the disorder is:

5 in 137,401 for profound biotinidase deficiency

- One in 109,921 for partial biotinidase deficiency

- One in 61,067 for the combined incidence of profound and partial biotinidase deficiency

- Carrier frequency in the general population is approximately one in 120.

Since biotin is in many foods at low concentrations, deficiency is rare except in locations where malnourishment is very common. Pregnancy, however, alters biotin catabolism and despite a regular biotin intake, half of the pregnant women in the U.S. are marginally biotin deficient.

Inherited or congenital FX deficiency is passed on by autosomal recessive inheritance. A person needs to inherit a defective gene from both parents. People who have only one defective gene usually do not exhibit the disease, but can pass the gene on to half their offspring. Different genetic mutations have been described.

In persons with congenital FX deficiency the condition is lifelong. People affected should alert other family members as they may also have the condition or carry the gene. In the general population the condition affects about 1 in 1 million people. However, the prevalence may be higher as not all individuals may express the disease and be diagnosed.

In the acquired form of FX deficiency an insufficient amount of factor X is produced by the liver due to liver disease, vitamin K deficiency, buildup of abnormal proteins in organs (amyloidosis) or certain medications (i.e. warfarin). In amyloidosis FX deficiency develops as FX and other coagulation factors are absorbed by amyloid fibrils.

Children with DOCK8 deficiency do not tend to live long; sepsis is a common cause of death at a young age. CNS and vascular complications are other common causes of death.

Folate is found in leafy green vegetables. Multi-vitamins also tend to include Folate as well as many other B vitamins. B vitamins, such as Folate, are water-soluble and excess is excreted in the urine.

When cooking, use of steaming, a food steamer, or a microwave oven can help keep more folate content in the cooked foods, thus helping to prevent folate deficiency.

Folate deficiency during human pregnancy has been associated with an increased risk of infant neural tube defects. Such deficiency during the first four weeks of gestation can result in structural and developmental problems. NIH guidelines recommend oral B vitamin supplements to decrease these risks near the time of conception and during the first month of pregnancy.

DOCK8 deficiency is very rare, estimated to be found in less than one person per million; there have been 32 patients diagnosed as of 2012.

By definition, primary immune deficiencies are due to genetic causes. They may result from a single genetic defect, but most are multifactorial. They may be caused by recessive or dominant inheritance. Some are latent, and require a certain environmental trigger to become manifest, like the presence in the environment of a reactive allergen. Other problems become apparent due to aging of bodily and cellular maintenance processes.

Factor X deficiency (X as Roman numeral ten) is a bleeding disorder characterized by a lack in the production of factor X (FX), an enzyme protein that causes blood to clot in the coagulation cascade. Produced in the liver FX when activated cleaves prothrombin to generate thrombin in the intrinsic pathway of coagulation. This process is vitamin K dependent and enhanced by activated factor V.

The condition may be inherited or, more commonly, acquired.

It can occur in patients with severely compromised intestinal function, those undergoing total parenteral nutrition, those who have had gastrointestinal bypass surgery, and also in persons of advanced age (i.e., over 90).

People dependent on food grown from selenium-deficient soil may be at risk for deficiency. Increased risk for developing various diseases has also been noted, even when certain individuals lack optimal amounts of selenium, but not enough to be classified as deficient.

For some time now, it has been reported in medical literature that a pattern of side-effects possibly associated with cholesterol-lowering drugs (e.g., statins) may resemble the pathology of selenium deficiency.

Pregnancy also poses as another high risk factor for vitamin D deficiency. The status levels of vitamin D during the last stages of pregnancy directly impact the new borns first initial months of life. Babies who are exclusively breastfed with minimal exposure to sunlight or supplementation can be at greater risk of vitamin D deficiency,as human milk has minimal vitamin D present. Recommendations for infants of the age 0–12 months are set at 5 ug/day, to assist in preventing rickets in young babies. 80% of dark skinned and or veiled women in Melbourne were found to have serum levels lower than 22.5 nmol/L considering them to be within moderate ranges of vitamin D deficiency.

Signs of vitamin E deficiency include the following:

- Neuromuscular problems-such as spinocerebellar ataxia and myopathies.

- Neurological problems-may include dysarthria, absence of deep tendon reflexes, loss of the ability to sense vibration and detect where body parts are in three dimensional space, and positive Babinski sign.

- Hemolytic anemia-due to oxidative damage to red blood cells

- Retinopathy

- Impairment of the immune response

There is also some laboratory evidence that vitamin E deficiency can cause male infertility.

Treatment of THB deficiencies consists of THB supplementation (2–20 mg/kg per day) or diet to control blood phenylalanine concentration and replacement therapy with neurotransmitters precursors (L-DOPA and 5-HTP) and supplements of folinic acid in DHPR deficiency.

Tetrahydrobiopterin is available as a tablet for oral administration in the form of "tetrahydrobiopterin dihydrochloride" (BH4*2HCL). BH4*2HCL is FDA approved under the trade name Kuvan. The typical cost of treating a patient with Kuvan is $100,000 per year. BioMarin holds the patent for Kuvan until at least 2024, but Par Pharmaceutical has a right to produce a generic version by 2020. BH4*2HCL is indicated at least in tetrahydrobiopterin deficiency caused by GTPCH deficiency or PTPS deficiency.

A survey of 10,000 American households revealed that the prevalence of diagnosed primary immunodeficiency approaches 1 in 1200. This figure does not take into account people with mild immune system defects who have not received a formal diagnosis.

Milder forms of primary immunodeficiency, such as selective immunoglobulin A deficiency, are fairly common, with random groups of people (such as otherwise healthy blood donors) having a rate of 1:600. Other disorders are distinctly more uncommon, with incidences between 1:100,000 and 1:2,000,000 being reported.

There is an increased risk of vitamin D deficiency in people who are considered overweight or obese based on their body mass index (BMI) measurement. The relationship between these conditions is not well understood. There are different factors that could contribute to this relationship, particularly diet and sunlight exposure. Alternatively, vitamin D is fat-soluble therefore excess amounts can be stored in fat tissue and used during winter, when sun exposure is limited.