The diagnosis is based on clinical features, with a concomitant decreased blood adenosine deaminase level supporting the diagnosis.

The diagnosis of Nezelof syndrome will indicate a deficiency of T-cells, additionally in ascertaining the condition the following is done:

The differential diagnosis for this condition consists of acquired immune deficiency syndrome and severe combined immunodeficiency syndrome

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.

Those affected with deficiency of the interleukin-1–receptor antagonist can have diagnosis achieved via noting an increase of erythrocyte sedimentation rate, as well as the following:

- Genetic test

- Radiological findings

- Clinical findings

The differential diagnosis for short-chain acyl-coenzyme A dehydrogenase deficiency is: ethylmalonic encephalopathy, mitochondrial respiratory chain defects and "multiple" acyl-CoA dehydrogenase deficiency.

Patients show markedly low immunoglobulin levels of IgG, IgA, and IgM.

The diagnosis of short-chain acyl-coenzyme A dehydrogenase deficiency is based on the following:

- Newborn screening test

- Genetic testing

- Urine test

On September 1990, the first gene therapy to combat this disease was performed by Dr. William French Anderson on a four-year-old girl, Ashanti DeSilva, at the National Institutes of Health, Bethesda, Maryland, U.S.A.

In April 2016 the Committee for Medicinal Products for Human Use of the European Medicines Agency endorsed and recommended for approval a stem cell gene therapy called Strimvelis, for children with ADA-SCID for whom no matching bone marrow donor is available.

The diagnosis of glycogen storage disease IX consists of the following:

- Complete blood count

- Urinalysis

- Histological study of the liver (via biopsy)

- Genetic testing

- Physical exam

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.

Most individuals with SBCADD are identified through newborn screening, where they present with an elevation of a five carbon acylcarnitine species. Confirmatory testing includes plasma and urine analysis to identify the carnitine and glycine conjugates of 2-methylbutyryl-CoA.

Upon clinical suspicion, diagnostic testing will often consist of measurement of amino acid concentrations in plasma, in search of a significantly elevated ornithine concentration. Measurement of urine amino acid concentrations is sometimes necessary, particularly in neonatal onset cases to identify the presence or absence of homocitrulline for ruling out ornithine translocase deficiency (hyperornithinemia, hyperammonemia, homocitrullinuria syndrome, HHH syndrome). Ornithine concentrations can be an unreliable indicator in the newborn period, thus newborn screening may not detect this condition, even if ornithine is included in the screening panel. Enzyme assays to measure the activity of ornithine aminotransferase can be performed from fibroblasts or lymphoblasts for confirmation or during the neonatal period when the results of biochemical testing is unclear. Molecular genetic testing is also an option.

There is a deficiency of malate in patients because fumarase enzyme can't convert fumarate into it therefore treatment is with oral malic acid which will allow the krebs cycle to continue, and eventually make ATP.

There are two types of this inherited condition, "glycogen storage disease IXa1" and "glycogen storage disease IXa2" that affect the liver of an individual. Mutations in PHKA2 have been seen in individuals with glycogen storage disease IXa2.

A small number of genetic variants have been repeatedly associated with DPD deficiency, such as IVS14+1G>A mutation in intron 14 coupled with exon 14 deletion (a.k.a. DPYD*2A), 496A>G in exon 6; 2846A>T in exon 22 and T1679G (a.k.a. DPYD*13) in exon 13. However, testing patients for these allelic variants usually show high specificity (i.e., bearing the mutation means that severe toxicity will occur indeed)but very low sentivity (i.e., not bearing the mutation does not mean that there is no risk for severe toxicities). Alternatively, phenotyping DPD using ex-vivo enzymatic assay or surrogate testing (i.e., monitoring physiological dihydrouracil to uracil ratio in plasma) has been presented as a possible upfront strategy to detect DPD deficiency. 5-FU test dose (i.e., preliminary administration of a small dose of 5-FU with pharmacokinetics evaluation) has been proposed as another possible alternative strategy to secure the use of fluoropyrimidine drugs.

In terms of treatment a 2013 review indicates that colchicine can be used for DIRA. Additionally there are several other management options such as anakinra, which blocks naturally occurring IL-1, this according to a 2016 pediatric textbook.

Elevated IgE is the hallmark of HIES. An IgE level greater than 2,000 IU/mL is often considered diagnostic. However, patients younger than 6 months of age may have very low to non-detectable IgE levels. Eosinophilia is also a common finding with greater than 90% of patients having eosinophil elevations greater than two standard deviations above the normal mean. Genetic testing is available for "STAT3" (Job's Syndrome), "DOCK8 (DOCK8 Immunodeficiency or DIDS)", "PGM3" (PGM3 deficiency), "SPINK5" (Netherton Syndrome - NTS), and "TYK2" genetic defects.

Brain MRI shows vermis atrophy or hypoplasic. Cerebral and cerebellar atrophy with white matter changes in some cases.

No cure currently exists; however, gene therapy has been proposed.

A new investigation has identified a seemingly successful treatment for LRBA deficiency by targeting CTLA4. Abatacept, an approved drug for rheumatoid arthritis, mimics the function of CTLA4 and has found to reverse life-threatening symptoms. The study included nine patients that exhibited improved clinical status and halted inflammatory conditions with minimal infectious or autoimmune complications. The study also suggests that therapies like chloroquine or hydroxychloroquine, which inhibit lysosomal degradation, may prove to be effective, as well. Larger cohorts are required to further validate these therapeutic approaches as effective long-term treatments for this disorder.

Most patients with hyper IgE syndrome are treated with long-term antibiotic therapy to prevent staphylococcal infections. Good skin care is also important in patients with hyper IgE syndrome. High-dose intravenous gamma-globulin has also been suggested for the treatment of severe eczema in patients with HIES and atopic dermatitis.

Onset of adult GM1 is between ages 3 and 30.

Symptoms include muscle atrophy, neurological complications that are less severe and progress at a slower rate than in other forms of the disorder, corneal clouding in some patients, and dystonia (sustained muscle contractions that cause twisting and repetitive movements or abnormal postures). Angiokeratomas may develop on the lower part of the trunk of the body. Most patients have a normal size liver and spleen.

Prenatal diagnosis is possible by measurement of Acid Beta Galactosidase in cultured amniotic cells.

Biotinidase deficiency can be found by genetic testing. This is often done at birth as part of newborn screening in several states throughout the United States. Results are found through testing a small amount of blood gathered through a heel prick of the infant. As not all states require that this test be done, it is often skipped in those where such testing is not required. Biotinidase deficiency can also be found by sequencing the "BTD" gene, particularly in those with a family history or known familial gene mutation.

MSD has an autosomal recessive inheritance pattern.

The inheritance probabilities "per birth" are as follows:

- If both parents are carriers:

- 25% (1 in 4) children will have the disorder

- 50% (2 in 4) children will be carriers (but unaffected)

- 25% (1 in 4) children will be free of MSD - unaffected child that is not a carrier

- If one parent is affected and one is free of MSD:

- 0% (0) children will have the disorder - only one parent is affected, other parent always gives normal gene

- 100% (4 in 4) children will be carriers (but unaffected)

- If one parent is a carrier and the other is free of MSD:

- 50% (2 in 4) children will be carriers (but unaffected)

- 50% (2 in 4) children will be free of MSD - unaffected child that is not a carrier