A diagnosis can only be definitively made after genetic testing to look for a mutation in the "DOCK8" gene. However, it can be suspected with a high IgE level and eosinophilia. Other suggestive laboratory findings include decreased numbers of B cells, T cells, and NK cells; and hypergammaglobulinemia. It can be distinguished from autosomal dominant hyper-IgE (STAT3 deficiency) because people with DOCK8 deficiency have low levels of IgM and an impaired secondary immune response. IgG and IgA levels are usually normal to high. It can be distinguished from the similar X-linked Wiskott–Aldrich syndrome by the presence of thrombocytopenia and the consequent bloody diarrhea, as well as its pattern of inheritance. WHIM syndrome, caused by a mutation in CXCR4, is associated with similar chronic cutaneous viral infections.

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.

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.

The diagnosis of hyper IgM syndrome can be done via the following methods and tests:

- MRI

- Chest radiography

- Pulmonary function test

- Lymph node test

- Laboratory test (to measure CD40)

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.

Five "types" of hyper IgM syndrome have been characterized:

- Hyper-IgM syndrome type 1 (X-linked), characterized by mutations of the "CD40LG" gene. In this type, T cells cannot tell B cells to switch classes.

- Hyper-IgM syndrome type 2 (autosomal recessive), characterized by mutations of the "AICDA" gene. In this type, B cells cannot recombine genetic material to change heavy chain production

- Hyper-IgM syndrome type 3 characterized by mutations of the "CD40" gene. In this type, B cells cannot receive the signal from T cells to switch classes.

- Hyper-IgM syndrome type 4 which is a defect in class switch recombination downstream of the AICDA gene that does not impair Somatic Hypermutation.

- Hyper-IgM syndrome type 5 characterized by mutations of the "UNG" gene.

Still's disease does not affect children under 6 months old.

Hyperimmunoglobulin D syndrome in 50% of cases is associated with mevalonate kinase deficiency which can be measured in the leukocytes.

The only treatment for Omenn syndrome is chemotherapy followed by a bone marrow transplantation. Without treatment, it is rapidly fatal in infancy.

The diagnosis is based on observing the patient and finding the constellation of symptoms and signs described above. A few blood tests help, by showing signs of long standing inflammation. There is no specific test for the disease, though now that the gene that causes the disease is known, that may change.

Routine laboratory investigations are non specific: anaemia, increased numbers of polymorphs, an elevated erythrocyte sedimentation rate and elevated concentrations of C-reactive protein are typically all the abnormalities found. Lumbar puncture shows elevated levels of polymorphs (20-70% of cases) and occasionally raised eosinophil counts (0-30% of cases). CSF neopterin may be elevated.

The X ray changes are unique and charactistic of this syndrome. These changes include bony overgrowth due to premature ossification of the patella and the long bone epiphyses in very young children and bowing of long bones with widening and shortening periosteal reaction in older ones.

Audiometry shows a progressive sensineural deafness. Visual examination shows optic atrophy and an increase in the blind spot. CT is usually normal but may show enlargement of the ventricles. MRI with contrast may show enhancement of leptomeninges and cochlea consistent with chronic meningitis. EEG shows is non specific with slow waves and spike discharges.

Polymorphs tend to show increased expression of CD10.

CDPX1 activity may be inhibited by warfarin because it is believed that ARSE has enzymatic activity in a vitamin K producing biochemical pathway. Vitamin K is also needed for controlling binding of calcium to bone and other tissues within the body.

The activity of arylsulfatase E can be measured with the substrate 4-methylumbelliferyl sulfate.

A review from 2000 stated that life expectancy was reduced because of a tendency to develop cancer relatively early as well as deaths due to infections related to immunodeficiency.

There is no treatment for NBS, however in those with agammaglobulinemia, intravenous immunoglobulin may be started. Prophylactic antibiotics are considered to prevent urinary tract infections as those with NBS often have congenital kidney malformations. In the treat of malignancies radiation, alkylating antineoplastic agents, and epipodophyllotoxins are not used, and methotrexate can be used with caution and, the dose should be limited. Bone marrow transplants and hematopoietic stem cells transplants are also considered in the treatment of NBS. The supplementation of Vitamin E is also recommended. A ventriculoperitoneal shunt can be placed in patients with hydrocephaly, and surgical intervention of congenital deformities is also attempted.

Alagille syndrome can be determined by a special kind of newborn screening wherein DNA samples are analyzed for markers in the JAG1 section. The DNA sequence patterns of a child will be analyzed for probabilistic deletions and therefore takes weeks to complete. After detection, the child should be treated with vitamins and necessary diet to develop the liver function postnatally.

In addition to genetic tests involving the sequencing of "PEX" genes, biochemical tests have proven highly effective for the diagnosis of Zellweger syndrome and other peroxisomal disorders. Typically, Zellweger syndrome patients show elevated very long chain fatty acids in their blood plasma. Cultured primarily skin fibroblasts obtained from patients show elevated very long chain fatty acids, impaired very long chain fatty acid beta-oxidation, phytanic acid alpha-oxidation, pristanic acid alpha-oxidation, and plasmalogen biosynthesis.

The disorder is thought to be related to mutations in the PDE3A gene.

The symptoms are very similar to graft-versus-host disease (GVHD). This is because the patients have some T cells with limited levels of recombination with the mutant RAG genes. These T cells are abnormal and have a very specific affinity for self antigens found in the thymus and in the periphery. Therefore, these T cells are auto-reactive and cause the GVHD phenotype.

A characteristic symptom is chronic inflammation of the skin, which appears as a red rash (early onset erythroderma). Other symptoms include eosinophilia, failure to thrive, swollen lymph nodes, swollen spleen, diarrhea, enlarged liver, low immunoglobulin levels (except immunoglobulin E, which is elevated), low T cell levels, and no B cells.

Hypertension and brachydactyly syndrome (HTNB) also known as Bilginturan syndrome and brachydactyly type E among others is a very rare genetic disorder.

It was first reported in 1973 by N. Bilginturan et al. The estimated prevalence is less than 1 out of 1,000,000.

People with yellow nail syndrome have been found to have a moderately reduced lifespan compared to people without the condition.

The diagnosis is based on the combination of the symptoms. Generally, people are diagnosed with yellow nail syndrome if they have two or three of the three classical symptoms (yellow nails, lymphedema and lung problems). The nail changes are considered essential for the diagnosis, but they can be subtle.

Pulmonary function testing can show obstruction of the airways. People with pleural effusions may show evidence of restriction in lung volumes due to the fluid. Analysis of the fluid in pleural effusions generally shows high levels of protein but low levels of cholesterol and lactate dehydrogenase, but about 30% of effusions are chylous (chylothorax) in that they have the characteristics of lymph.

A lymphogram may be performed in people with lymphedema. This can show both under developed (hypoplastic) lymphatic ducts and dilated ducts. Dye may be found in the skin months after the initial test. Scintigraphy of lymph flow (lymphoscintigraphy) shows delays in drainage of lymph (sometimes asymmetrically), although this test can also be normal.

The malabsorption resulting from lack of bile acid has resulted in elemental formula being suggested, which are low in fat with < 3% of calories derived from long chain triglycerides (LCT). However, reduced very long chain fatty acids (VLCFA) has not been shown to reduce blood VLCFA levels , likely because humans can endogenously produce most VLCFA. Plasma VLCFA levels are decreased when dietary VLCFA is reduced in conjunction with supplementation of Lorenzo’s oil (a 4:1 mixture of glyceryl trioleate and glyceryl trierucate) in X-ALD patients . Since docosahexaenoic acid (DHA) synthesis is impaired [59], DHA supplementation was recommended, but a placebo-controlled study has since showed no clinical efficacy . Due to the defective bile acid synthesis, fat soluble supplements of vitamins, A, D, E, and K are recommended.

Early treatment is possible once the disease is detected. Once the classical symptoms appear, the best way to eliminate the dangers of Alagille syndrome is a full liver transplant. Most of the short-term treatments available are aimed at improving the functioning of the heart and reducing the effects of impaired liver, kidney, and spleen function.

There are 3 possible ways to test the fetal antigen status. Free Cell DNA, Amniocentesis, and Chorionic Villus Sampling. Of the three, CVS is no longer used due to risk of worsening the maternal antibody response. Once antigen status has been determined, assessment may be done with MCA scans.

- Free Cell DNA can be run on certain antigens. Blood is taken from the mother, and using PCR, can detect the K, C, c, D, and E alleles of fetal DNA. This blood test is non-invasive to the fetus and is an easy way of checking antigen status and risk of HDN. Testing has proven very accurate and is routinely done in the UK at the International Blood Group Reference Laboratory in Bristol. Sanequin laboratory in Amsterdam, Netherlands also performs this test. For US patients, blood may be sent to either of the labs. In the US, Sensigene is done by Sequenome to determine fetal D status. Sequenome does not accept insurance in the US, but US and Canadian patients have had insurance cover the testing done overseas.

- Amniocentesis is another recommended method for testing antigen status and risk for HDN. Fetal antigen status can be tested as early as 15 weeks by PCR of fetal cells.

- CVS is possible as well to test fetal antigen status but is not recommended. CVS carries a higher risk of fetal maternal hemorrhage and can raise antibody titers, potentially worsening the antibody effect.

The initial workup of abetalipoproteinemia typically consists of stool sampling, a blood smear, and a fasting lipid panel though these tests are not confirmatory. As the disease is rare, though a genetics test is necessary for diagnosis, it is generally not done initially.

Acanthocytes are seen on blood smear. Since there is no or little assimilation of chylomicrons, their levels in plasma remains low.

The inability to absorb fat in the ileum will result in steatorrhea, or fat in the stool. As a result, this can be clinically diagnosed when foul-smelling stool is encountered. Low levels of plasma chylomicron are also characteristic.

There is an absence of apolipoprotein B. On intestinal biopsy, vacuoles containing lipids are seen in enterocytes. This disorder may also result in fat accumulation in the liver (hepatic steatosis). Because the epithelial cells of the bowel lack the ability to place fats into chylomicrons, lipids accumulate at the surface of the cell, crowding the functions that are necessary for proper absorption.

In some cases, the direct coombs will be negative but severe, even fatal HDN can occur. An indirect coombs needs to be run in cases of anti-C, anti-c, and anti-M. Anti-M also recommends antigen testing to rule out the presence of HDN.