Whether MTHFR deficiency has any effect at all on all-cause mortality is unclear. One Dutch study showed that the MTHFR mutation was more prevalent in younger individuals (36% relative to 30%), and found that elderly men with MTHFR had an elevated mortality rate, attributable to cancer. Among women, however, no difference in life expectancy was seen. More recently, however, a meta-analysis has shown that overall cancer rates are barely increased with an odds ratio of 1.07, which suggests that an impact on mortality from cancer is small or zero.

Infusions of immune globulin can reduce the frequency of bacterial infections, and G-CSF or GM-CSF therapy improves blood neutrophil counts.

As WHIM syndrome is a molecular disease arising from gain-of-function mutations in CXCR4, preclinical studies identified plerixafor, a specific CXCR4 antagonist, as a potential mechanism-based therapeutic for the disease. Two subsequent clinical trials involving a handful of patients with WHIM syndrome demonstrated that plerixafor could increase white blood cell counts and continues to be a promising targeted therapy.

A woman with spontaneous remission of her WHIM syndrome due to Chromothripsis in one of her blood stem cells has been identified.

In support of these studies, a 2014 phase I clinical trial treated 3 patients diagnosed with WHIM syndrome with plerixafor twice a day for 6 months. All three patients presented with multiple reoccurring infections before treatment and all had an increase in their white blood cell count post treatment. One patient (P3) had a decrease in his infections by 40% while the remaining 2 patients (P1 and P2) had no infections throughout the entirety of the treatment. Plerixafor may also proof to have anti-human papillomavirus (HPV) properties as all patients experienced a shrinkage or complete disappearance of their warts. While this treatment shows promise in treating neutropenia (decreased white blood cells), this trial showed no increase of immune globulins in the body. A phase III clinical trial has been approved to compare the infection prevention ability of plerixafor versus the current treatment of G-CSF in patients with WHIM.

Patients exhibit increased susceptibility to bacterial and viral infections, especially from common serotype human papilloma virus, resulting in warts on the hands and feet starting in childhood. Myelokathexis refers to retention (kathexis) of neutrophils in the bone marrow (myelo). In addition, lymphocytes and IgG antibody levels (gammaglobulins) are often deficient.

The prevalence of 677T homozygozity varies with race. 18-21% of Hispanics and Southern Mediterranean populations have this variant, as do 6-14% of North American Caucasians and <2% of Blacks living outside of Africa.

The prevalence of the 1298C mutation is lower, at 4-12% for most tested populations.

A study in 2000 had identified only 24 cases of severe MTHFR deficiency (from nonsense mutations) across the whole world.

Diagnosis: A special urine test is available to check for any partially broken-down-sugars. If they are present, a skin or blood sample will be taken to test for below-normal amounts of alpha-fucosidase.

- Fucosidosis is an autosomal recessive disorder, which means that both parents have to have the mutation and pass it on to the child. When both parents have the mutation, there is a 25% chance of each child having fucosidosis.

The World Anti-Doping Agency (WADA) is the main regulatory organization looking into the issue of the detection of gene doping. Both direct and indirect testing methods are being researched by the organization. Directly detecting the use of gene therapy usually requires the discovery of recombinant proteins or gene insertion vectors, while most indirect methods involve examining the athlete in an attempt to detect bodily changes or structural differences between endogenous and recombinant proteins.

Indirect methods are by nature more subjective, as it becomes very difficult to determine which anomalies are proof of gene doping, and which are simply natural, though unusual, biological properties. For example, Eero Mäntyranta, an Olympic cross country skier, had a mutation which made his body produce abnormally high amounts of red blood cells. It would be very difficult to determine whether or not Mäntyranta's red blood cell levels were due to an innate genetic advantage, or an artificial one.

Type 2 appears when a child is around 18 months of age and in considered milder than Type 1 but still severe. Symptoms include:

- Symptoms similar to Type 1 but milder and progress more slowly.

A triplex tetra-primer ARMS-PCR method was developed for the simultaneous detection of C677T and A1298C polymorphisms with the A66G MTRR polymorphism in a single PCR reaction.

The World Anti-Doping Agency (WADA) determined that non therapeutic form of genetic manipulation for enhancement of athletic performance is not allowed in sport. The WADA code implemented guidelines to determine if said technology should be prohibited in sport. If two of the three conditions are met, then the technology is prohibited in sport; harmful to one's health, performance enhancing, and/or against the "spirit of sport". The high risks associated with gene therapy can be outweighed by the potential save the lives of individuals with diseases. According to Alain Fischer, who was involved in clinical trials of gene therapy in children with severe combined immunodeficiency, "Only people who are dying would have reasonable grounds for using it. Using gene therapy for doping is ethically unacceptable and scientifically stupid." As seen with past cases, including the steroid tetrahydrogestrinone THG, athletes may choose to incorporate risky genetic technologies into their training regimes.

The mainstream perspective is that gene doping is dangerous and unethical, as is any application of a therapeutic intervention for non-therapeutic or enhancing purposes, and that it compromises the ethical foundation of medicine and the spirit of sport. Others, who support human enhancement on broader grounds, or who see a false dichotomy between "natural" and "artificial" or a denial of the role of technology in improving athletic performance, do not oppose or support gene doping.

Opinions differ about optimal screening and diagnostic measures, in part due to differences in population risks, cost-effectiveness considerations, and lack of an evidence base to support large national screening programs. The most elaborate regimen entails a random blood glucose test during a booking visit, a screening glucose challenge test around 24–28 weeks' gestation, followed by an OGTT if the tests are outside normal limits. If there is a high suspicion, a woman may be tested earlier.

In the United States, most obstetricians prefer universal screening with a screening glucose challenge test. In the United Kingdom, obstetric units often rely on risk factors and a random blood glucose test. The American Diabetes Association and the Society of Obstetricians and Gynaecologists of Canada recommend routine screening unless the woman is low risk (this means the woman must be younger than 25 years and have a body mass index less than 27, with no personal, ethnic or family risk factors) The Canadian Diabetes Association and the American College of Obstetricians and Gynecologists recommend universal screening. The U.S. Preventive Services Task Force found there is insufficient evidence to recommend for or against routine screening.

Some pregnant women and careproviders choose to forgo routine screening due to the absence of risk factors, however this is not advised due to the large proportion of women who develop gestational diabetes despite having no risk factors present and the dangers to the mother and baby if gestational diabetes remains untreated.

The diagnosis of A-T is usually suspected by the combination of neurologic clinical features (ataxia, abnormal control of eye movement, and postural instability) with telangiectasia and sometimes increased infections, and confirmed by specific laboratory abnormalities (elevated alpha-fetoprotein levels, increased chromosomal breakage or cell death of white blood cells after exposure to X-rays, absence of ATM protein in white blood cells, or mutations in each of the person’s ATM genes).

A variety of laboratory abnormalities occur in most people with A-T, allowing for a tentative diagnosis to be made in the presence of typical clinical features. Not all abnormalities are seen in all patients. These abnormalities include:

- Elevated and slowly increasing alpha-fetoprotein levels in serum after 2 years of age

- Immunodeficiency with low levels of immunoglobulins (especially IgA, IgG subclasses, and IgE) and low number of lymphocytes in the blood

- Chromosomal instability (broken pieces of chromosomes)

- Increased sensitivity of cells to x-ray exposure (cells die or develop even more breaks and other damage to chromosomes)

- Cerebellar atrophy on MRI scan

The diagnosis can be confirmed in the laboratory by finding an absence or deficiency of the ATM protein in cultured blood cells, an absence or deficiency of ATM function (kinase assay), or mutations in both copies of the cell’s ATM gene. These more specialized tests are not always needed, but are particularly helpful if a child’s symptoms are atypical.

Marshall–Smith syndrome is not to be confused with:

- Marshall syndrome (aka.Periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA syndrome, see also: Periodic fever syndrome)

- Sotos (like) syndrome

- Weaver-Smith syndrome (WSS)

Respiratory complications are often cause of death in early infancy.

Hypergammaglobulinemia is a medical condition with elevated levels of gamma globulin.

It is a type of immunoproliferative disorder.

Severe MTHFR deficiency is rare (about 50 cases worldwide) and caused by mutations resulting in 0–20% residual enzyme activity. Patients exhibit developmental delay, motor and gait dysfunction, seizures, and neurological impairment and have extremely high levels of homocysteine in their plasma and urine as well as low to normal plasma methionine levels.

A study on the Chinese Uyghur population indicated that rs1801131 polymorphism in MTHFR was associated with nsCL/P in Chinese Uyghur population. Given the unique genetic and environmental characters of the Uyghur population, these findings may be helpful for exploring the pathogenesis of this complex disease.

Hypergammaglobulinemia is a condition that is characterized by the increased levels of a certain immunoglobulin in the blood serum. The name of the disorder refers to an excess of proteins after serum protein electrophoresis (found in the gammaglobulin region).

Most hypergammaglobulinemias are caused by an excess of immunoglobulin M (IgM), because this is the default immunoglobulin type prior to class switching. Some types of hypergammaglobulinemia are actually caused by a deficiency in the other major types of immunoglobulins, which are IgA, IgE and IgG.

There are 5 types of hypergammaglobulinemias associated with hyper IgM.

MeSH considers hyper IgM syndrome to be a form of dysgammaglobulinemia, not a form of hypergammaglobulinemia .

Women with GDM may have high glucose levels in their urine (glucosuria). Although dipstick testing is widely practiced, it performs poorly, and discontinuing routine dipstick testing has not been shown to cause underdiagnosis where universal screening is performed. Increased glomerular filtration rates during pregnancy contribute to some 50% of women having glucose in their urine on dipstick tests at some point during their pregnancy. The sensitivity of glucosuria for GDM in the first 2 trimesters is only around 10% and the positive predictive value is around 20%.

RAPADILINO syndrome is an autosomal recessive disorder characterized by:

- RA: radial ray defect

- PA: patellar aplasia, arched or cleft palate

- DI: diarrhea, dislocated joints

- LI: little size (short stature), limb malformation

- NO: nose slender and normal intelligence.

It is more prevalent in Finland than elsewhere in the world.

It has been associated with the gene RECQL4. This is also associated with Rothmund-Thomson syndrome and Baller-Gerold syndrome.

All individuals with A-T should have at least one comprehensive immunologic evaluation that measures the number and type of lymphocytes in the blood (T-lymphocytes and B-lymphocytes), the levels of serum immunoglobulins (IgG, IgA, and IgM) and antibody responses to T-dependent (e.g., tetanus, Hemophilus influenzae b) and T-independent (23-valent pneumococcal polysaccharide) vaccines. For the most part, the pattern of immunodeficiency seen in an A-T patient early in life (by age five) will be the same pattern seen throughout the lifetime of that individual. Therefore, the tests need not be repeated unless that individual develops more problems with infection. Problems with immunity sometimes can be overcome by immunization. Vaccines against common bacterial respiratory pathogens such as Hemophilus influenzae, pneumococci and influenza virus (the “flu”) are commercially available and often help to boost antibody responses, even in individuals with low immunoglobulin levels. If the vaccines do not work and the patient continues to have problems with infections, gamma globulin therapy (IV or subcutaneous infusions of antibodies collected from normal individuals) may be of benefit. A small number of people with A-T develop an abnormality in which one or more types of immunoglobulin are increased far beyond the normal range. In a few cases, the immunoglobulin levels can be increased so much that the blood becomes thick and does not flow properly. Therapy for this problem must be tailored to the specific abnormality found and its severity.

If an individual patient’s susceptibility to infection increases, it is important to reassess immune function in case deterioration has occurred and a new therapy is indicated. If infections are occurring in the lung, it is also important to investigate the possibility of dysfunctional swallow with aspiration into the lungs (see above sections under Symptoms: Lung Disease and Symptoms: Feeding, Swallowing and Nutrition.)

Most people with A-T have low lymphocyte counts in the blood. This problem seems to be relatively stable with age, but a rare number of people do have progressively decreasing lymphocyte counts as they get older. In the general population, very low lymphocyte counts are associated with an increased risk for infection. Such individuals develop complications from live viral vaccines (measles, mumps, rubella and chickenpox), chronic or severe viral infections, yeast infections of the skin and vagina, and opportunistic infections (such as pneumocystis pneumonia). Although lymphocyte counts are often as low in people with A-T, they seldom have problems with opportunistic infections. (The one exception to that rule is that problems with chronic or recurrent warts are common.) The number and function of T-lymphocytes should be re-evaluated if a person with A-T is treated with corticosteroid drugs such as prednisone for longer than a few weeks or is treated with chemotherapy for cancer. If lymphocyte counts are low in people taking those types of drugs, the use of prophylactic antibiotics is recommended to prevent opportunistic infections.

If the tests show significant abnormalities of the immune system, a specialist in immunodeficiency or infectious diseases will be able to discuss various treatment options. Absence of immunoglobulin or antibody responses to vaccine can be treated with replacement gamma globulin infusions, or can be managed with prophylactic antibiotics and minimized exposure to infection. If antibody function is normal, all routine childhood immunizations including live viral vaccines (measles, mumps, rubella and varicella) should be given. In addition, several “special” vaccines (that is, licensed but not routine for otherwise healthy children and young adults) should be given to decrease the risk that an A-T patient will develop lung infections. The patient and all household members should receive the influenza (flu) vaccine every fall. People with A-T who are less than two years old should receive three (3) doses of a pneumococcal conjugate vaccine (Prevnar) given at two month intervals. People older than two years who have not previously been immunized with Prevnar should receive two (2) doses of Prevnar. At least 6 months after the last Prevnar has been given and after the child is at least two years old, the 23-valent pneumococcal vaccine should be administered. Immunization with the 23-valent pneumococcal vaccine should be repeated approximately every five years after the first dose.

In people with A-T who have low levels of IgA, further testing should be performed to determine whether the IgA level is low or completely absent. If absent, there is a slightly increased risk of a transfusion reaction. “Medical Alert” bracelets are not necessary, but the family and primary physician should be aware that if there is elective surgery requiring red cell transfusion, the cells should be washed to decrease the risk of an allergic reaction.

People with A-T also have an increased risk of developing autoimmune or chronic inflammatory diseases. This risk is probably a secondary effect of their immunodeficiency and not a direct effect of the lack of ATM protein. The most common examples of such disorders in A-T include immune thrombocytopenia (ITP), several forms of arthritis, and vitiligo.

To date there is no treatment for ocular albinism, probably because little is known about the receptor function and its role in the pathophysiology of the condition. Though surgery for strabismus is sometimes helpful, there does not seem to be a sure remedy for it until the cause of ocular albinism is well established. However, with the recent discovery of the upstream ligand (L-DOPA) and the discovery of Oa1's possible downstream G alpha partner (Gai3) the Oa1 pathway is becoming clearer and future of Oa1 research looks promising.

Touloukian "et al." have characterized OA1 immunologically as a melanoma/melanocyte differentiation antigen. Flow cytometry data suggests that OA1-specific T cells are all CD8+. This indicates that OA1 peptide is processed and presented on the surface of melanoma cells to be recognized by antigen-specific T cells. Moreover, recognition of OA1 by T cells induces cytokine production by the OA1-specific T cells. This means that OA1 is a potential target for melanoma vaccines.

Though only definitively diagnosable by genetic sequence testing, including a G band analysis, ATR-16 syndrome may be diagnosed from its constellation of symptoms. It must be distinguished from ATR-X syndrome, a very similar disease caused by a mutation on the X chromosome, and cases of alpha-thalassemia that co-occur with intellectual disabilities with no underlying genetic relationship.

Because the cause is unknown, no effective preventive measures can be taken.

Because the disease is rare, routine screening is not cost-effective.

The diagnosis of androgenic alopecia can be usually established based on clinical presentation in men. In women, the diagnosis usually requires more complex diagnostic evaluation. Further evaluation of the differential requires exclusion of other causes of hair loss, and assessing for the typical progressive hair loss pattern of androgenic alopecia. Trichoscopy can be used for further evaluation. Biopsy may be needed to exclude other causes of hair loss, and histology would demonstrate perifollicular fibrosis.

Branchio-oculo-facial syndrome is difficult to diagnose because it has incomplete penetrance. It is often misdiagnosed as branchio-oto-renal syndrome because of their similarities in symptoms.

It was estimated that only about 50 cases of BOFS have been documented in the medical literature as of 2004.