A 2009 study reported results from 36 children who had received a stem cell transplant. At the time of follow-up (median time 62 months), 75% of the children were still alive.

LAD is a rare disease, with an estimated prevalence of one in 100,000 births, with no described racial or ethnic predilection. The most common type is LAD1.

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.

LAD1 is caused by mutations in the ITGB2 gene which are inherited autorecessively. This gene encodes CD18, a protein present in several cell surface receptor complexes found on white blood cells, including lymphocyte function-associated antigen 1 (LFA-1), complement receptor 3 (CR-3), and complement receptor 4 (CR-4). The deficiency of LFA-1 causes neutrophils to be unable to adhere to and migrate out of blood vessels, so their counts can be high. It also impairs immune cell interaction, immune recognition, and cell-killing lymphocyte functions. The lack of CR3 interferes with chemotaxis, phagocytosis, and respiratory burst.

Because the CD18 gene has been cloned and sequenced, this disorder is a potential candidate for gene therapy.

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.

This type of GvHD is associated with transfusion of un-irradiated blood to immunocompromised recipients. It can also occur in situations in which the blood donor is homozygous and the recipient is heterozygous for an HLA haplotype. It is associated with higher mortality (80-90%) due to involvement of bone marrow lymphoid tissue, however the clinical manifestations are similar to GVHD resulting from bone marrow transplantation. Transfusion-associated GvHD is rare in modern medicine. It is almost entirely preventable by controlled irradiation of blood products to inactivate the white blood cells (including lymphocytes) within.

Neutrophilia is an increase in the absolute neutrophil count in the peripheral circulation. Normal blood values vary by age. Neutrophilia can be caused by a direct problem with blood cells (primary disease). It can also occur as a consequence of an underlying disease (secondary). Most cases of neutrophilia are secondary to inflammation.

Primary causes

- Conditions with normally functioning neutrophils – hereditary neutrophilia, chronic idiopathic neutrophilia

- Pelger–Huet anomaly

- Down syndrome

- Leukocyte adhesion deficiency

- Familial cold urticaria

- Leukemia (chronic myelogenous (CML)) and other myeloproliferative disorders

- Surgical removal of spleen

Secondary causes

- Infection

- Chronic inflammation – especially juvenile rheumatoid arthritis, rheumatoid arthritis, Still's disease, Crohn's disease, ulcerative colitis, granulomatous infections (for example, tuberculosis), and chronic hepatitis

- Cigarette smoking – occurs in 25–50% of chronic smokers and can last up to 5 years after quitting

- Stress – exercise, surgery, general stress

- Medication induced – corticosteroids (for example, prednisone, β-agonists, lithium)

- Cancer – either by growth factors secreted by the tumor or invasion of bone marrow by the cancer

- Increased destruction of cells in peripheral circulation can stimulate bone marrow. This can occur in hemolytic anemia and idiopathic thrombocytopenic purpura

Congenital disorder of glycosylation type IIc or Leukocyte adhesion deficiency-2 (LAD2) is a type of leukocyte adhesion deficiency attributable to the absence of neutrophil sialyl-LewisX, a ligand of P- and E-selectin on vascular endothelium. It is associated with "SLC35C1".

This disorder was discovered in two unrelated Israeli boys 3 and 5 years of age, each the offspring of consanguineous parents. Both had severe mental retardation, short stature, a distinctive facial appearance, and the Bombay (hh) blood phenotype, and both were secretor- and Lewis-negative. They both had had recurrent severe bacterial infections similar to those seen in patients with LAD1, including pneumonia, peridontitis, otitis media, and localized cellulitis. Similar to that in patients with LAD1, their infections were accompanied by pronounced leukocytosis (30,000 to 150,000/mm) but an absence of pus formation at sites of recurrent cellulitis. In vitro studies revealed a pronounced defect in neutrophil motility. Because the genes for the red blood cell H antigen and for the secretor status encode for distinct α1,2-fucosyltransferases and the synthesis of Sialyl-LewisX requires an α1,3-fucosyltransferase, it was postulated that a general defect in fucose metabolism is the basis for this disorder. It was subsequently found that GDP-L-fucose transport into Golgi vesicles was specifically impaired, and then missense mutations in the GDP-fucose transporter cDNA of three patients with LAD2 were discovered. Thus, GDP-fucose transporter deficiency is a cause of LAD2.

Primary immune deficiency diseases are those caused by inherited genetic mutations. Secondary or acquired immune deficiencies are caused by something outside the body such as a virus or immune suppressing drugs.

Primary immune diseases are at risk to an increased susceptibility to, and often recurrent ear infections, pneumonia, bronchitis, sinusitis or skin infections. Immunodeficient patients may less frequently develop abscesses of their internal organs, autoimmune or rheumatologic and gastrointestinal problems.

- Primary immune deficiencies

- Severe combined immunodeficiency (SCID)

- DiGeorge syndrome

- Hyperimmunoglobulin E syndrome (also known as Job’s Syndrome)

- Common variable immunodeficiency (CVID): B-cell levels are normal in circulation but with decreased production of IgG throughout the years, so it is the only primary immune disorder that presents onset in the late teens years.

- Chronic granulomatous disease (CGD): a deficiency in NADPH oxidase enzyme, which causes failure to generate oxygen radicals. Classical recurrent infection from catalase positive bacteria and fungi.

- Wiskott-Aldrich syndrome (WAS)

- Autoimmune lymphoproliferative syndrome (ALPS)

- Hyper IgM syndrome: X-linked disorder that causes a deficiency in the production of CD40 ligand on activated T-cells. This increases the production and release of IgM into circulation. The B-cell and T-cell numbers are within normal limits. Increased susceptibility to extracellular bacteria and opportunistic infections.

- Leukocyte adhesion deficiency (LAD)

- NF-κB Essential Modifier (NEMO) Mutations

- Selective immunoglobulin A deficiency: the most common defect of the humoral immunity, characterized by a deficiency of IgA. Produces repeating sino-pulmonary and gastrointestinal infections.

- X-linked agammaglobulinemia (XLA; also known as Bruton type agammaglobulinemia): characterized by a deficiency in tyrosine kinase enzyme that blocks B-cell maturation in the bone marrow. No B-cells are produced to circulation and thus, there are no immunoglobulin classes, although there tends to be a normal cell-mediated immunity.

- X-linked lymphoproliferative disease (XLP)

- Ataxia-telangiectasia

- Secondary immune deficiencies

- AIDS

An allergy is an abnormal immune reaction to a harmless antigen.

- Seasonal allergy

- Mastocytosis

- Perennial allergy

- Anaphylaxis

- Food allergy

- Allergic rhinitis

- Atopic dermatitis

Graft-versus-host disease (GvHD) is a medical complication following the receipt of transplanted tissue from a genetically different person. GvHD is commonly associated with stem cell transplant (bone marrow transplant), but the term also applies to other forms of tissue graft. Immune cells (white blood cells) in the donated tissue (the graft) recognize the recipient (the host) as foreign (nonself). The transplanted immune cells then attack the host's body cells. GvHD can also occur after a blood transfusion if the blood products used have not been irradiated or treated with an approved pathogen reduction system.

Whereas transplant rejection occurs when the host rejects the graft, GvHD occurs when the graft rejects the host. The underlying principle (alloimmunity) is the same, but the details and course may differ.

Neutrophils are the primary white blood cells that respond to a bacterial infection, so the most common cause of neutrophilia is a bacterial infection, especially pyogenic infections.

Neutrophils are also increased in any acute inflammation, so will be raised after a heart attack, other infarct or burns.

Some drugs, such as prednisone, have the same effect as cortisol and adrenaline (epinephrine), causing marginated neutrophils to enter the blood stream. Nervousness will very slightly raise the neutrophil count because of this effect.

A neutrophilia might also be the result of a malignancy. Chronic myelogenous leukemia (CML or chronic myeloid leukaemia) is a disease where the blood cells proliferate out of control. These cells may be neutrophils. Neutrophilia can also be caused by appendicitis and splenectomy.

Primary neutrophilia can additionally be a result of Leukocyte adhesion deficiency.

Neutrophilia (also called neutrophil leukocytosis or occasionally neutrocytosis) is leukocytosis of neutrophils, that is, a high number of neutrophil granulocytes in the blood.

Neutropenia can be acquired or intrinsic. A decrease in levels of neutrophils on lab tests is due to either decreased production of neutrophils or increased removal from the blood. The following list of causes is not complete.

- Medications - chemotherapy, sulfas or other antibiotics, phenothiazenes, benzodiazepines, antithyroids, anticonvulsants, quinine, quinidine, indomethacin, procainamide, thiazides

- Radiation

- Toxins - alcohol, benzenes

- Intrinsic disorders - Fanconi's, Kostmann's, cyclic neutropenia, Chédiak–Higashi

- Immune dysfunction - disorders of collagen, AIDS, rheumatoid arthritis

- Blood cell dysfunction - megaloblastic anemia, myelodysplasia, marrow failure, marrow replacement, acute leukemia

- Any major infection

- Miscellaneous - starvation, hypersplenism

Symptoms of neutropenia are associated with the underlying cause of the decrease in neutrophils. For example, the most common cause of acquired neutropenia is drug-induced, so an individual may have symptoms of medication overdose or toxicity.

Treatment is also aimed at the underlying cause of the neutropenia. One severe consequence of neutropenia is that it can increase the risk of infection.

In many cases, MHA requires no treatment. However, in extreme cases, blood platelet transfusions may be necessary

Monocytosis is the state of excess monocytes in the peripheral blood. It may be indicative of various disease states.

Examples of processes that can increase a monocyte count include:

- chronic inflammation

- stress response

- Cushing's syndrome (hyperadrenocorticism)

- immune-mediated disease

- granulomatous disease

- atherosclerosis

- necrosis

- red blood cell regeneration

- viral fever

- sarcoidosis

A high count of CD14+CD16++ monocytes is found in severe infection (sepsis)

In the field of atherosclerosis high numbers of the CD14++CD16+ intermediate monocytes were shown to be predictive of cardiovascular events in at risk populations.

Pelger–Huët anomaly (pronunciation: [pel′gər hyo̅o̅′ət]) is a blood laminopathy associated with the lamin B receptor.

It is characterized by a white blood cell type known as a neutrophil whose nucleus is hyposegmented.

It is a genetic disorder with an autosomal dominant inheritance pattern. Heterozygotes are clinically normal, although their neutrophils may be mistaken for immature cells which may cause mistreatment in a clinical setting. Homozygotes tend to have neutrophils with rounded nuclei that do have some functional problems.

As noted above, a leukemoid reaction is typically a response to an underlying medical issue. Causes of leukemoid reactions include:

- Severe hemorrhage (retroperitoneal hemorrhage)

- Drugs

- Use of sulfa drugs

- Use of dapsone

- Use of glucocorticoids

- Use of G-CSF or related growth factors

- All-trans retinoic acid (ATRA)

- Ethylene glycol intoxication

- Infections

- Clostridium difficile

- Tuberculosis

- Pertussis

- Infectious mononucleosis (lymphocyte predominant)

- Visceral larva migrans (eosinophil predominant)

- Asplenia

- Diabetic ketoacidosis

- Organ necrosis

- Hepatic necrosis

- Ischemic colitis

- As a feature of trisomy 21 in infancy (incidence of ~10%)

- As a paraneoplastic phenomenon (rare)

MHA is believed to be associated with the "MYH9" gene. The pathogenesis of the disorder had been unknown until recently, when autosomal dominant mutations in the gene encoding non-muscle myosin heavy chain IIA ("MYH9") were identified. Unique cytoplasmic inclusion bodies are aggregates of nonmuscle myosin heavy chain IIA, and are only present in granulocytes. It is not yet known why inclusion bodies are not present in platelets, monocytes, and lymphocytes, or how giant platelets are formed. "MYH9" is also found to be responsible for several related disorders with macrothrombocytopenia and leukocyte inclusions, including Sebastian, Fechtner, and Epstein syndromes, which feature deafness, nephritis, and/or cataract. MHA is also a feature of the Alport syndrome (hereditary nephritis with sensorineural hearing loss).

Is a benign dominantly inherited defect of terminal neutrophil differentiation as a result of mutations in the lamin B receptor gene. The characteristic leukocyte appearance was first reported in 1928 by Karel Pelger (1885-1931), a Dutch Hematologist, who described leukocytes with dumbbell-shaped bilobed nuclei, a reduced number of nuclear segments, and coarse clumping of the nuclear chromatin. In 1931, Gauthier Jean Huet (1879-1970), a Dutch Pediatrician, identified it as an inherited disorder.

It is a genetic disorder with an autosomal dominant inheritance pattern. Heterozygotes are clinically normal, although their neutrophils may be mistaken for immature cells, which may cause mistreatment in a clinical setting. Homozygotes tend to have neutrophils with rounded nuclei that do have some functional problems. Homozygous individuals inconsistently have skeletal anomalies such as post-axial polydactyly, short metacarpals, short upper limbs, short stature, or hyperkyphosis.

Identifying Pelger–Huët anomaly is important to differentiate from bandemia with a left-shifted peripheral blood smear and neutrophilic band forms and from an increase in young neutrophilic forms that can be observed in association with infection.

The term leukemoid reaction describes an increased

white blood cell count, or leukocytosis, which is a physiological response to stress or infection (as opposed to a primary blood malignancy, such as leukemia). It often describes the presence of immature cells such as myeloblasts or red blood cells with nuclei in the peripheral blood.

It may be lymphoid or myeloid.

Inflammatory Linear Verrucous Epidermal Nevus (ILVEN) is a rare disease of the skin that presents as multiple, discrete, red papules that tend to coalesce into linear plaques that follow the Lines of Blaschko. The plaques can be slightly warty (psoriaform) or scaly (eczema-like). ILVEN is caused by somatic mutations that result in genetic mosaicism. There is no cure, but different medical treatments can alleviate the symptoms.

Monocytopenia is a form of leukopenia associated with a deficiency of monocytes.

A very low count of these cells is found after therapy with immuno-suppressive glucocorticoids.

Also, non-classical slan+ monocytes are strongly reduced in patients with hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS), a neurologic disease associated

with mutations in the macrophage colony-stimulating factor receptor gene.

An increase in eosinophils, i.e., the presence of more than 500 eosinophils/microlitre of blood is called an eosinophilia, and is typically seen in people with a parasitic infestation of the intestines; autoimmune and collagen vascular disease (such as rheumatoid arthritis) and Systemic lupus erythematosus; malignant diseases such as eosinophilic leukemia, clonal hypereosinophilia, and Hodgkin's disease; lymphocyte-variant hypereosinophilia; extensive skin diseases (such as exfoliative dermatitis); Addison's disease and other causes of low corticosteroid production (corticosteroids suppress blood eosinophil levels); reflux esophagitis (in which eosinophils will be found in the squamous epithelium of the esophagus) and eosinophilic esophagitis; and with the use of certain drugs such as penicillin. But, perhaps the most common cause for eosinophilia is an allergic condition such as asthma. In 1989, contaminated L-tryptophan supplements caused a deadly form of eosinophilia known as eosinophilia-myalgia syndrome, which was reminiscent of the Toxic Oil Syndrome in Spain in 1981.

Eosinophils play an important role in asthma as the number of accumulated eosinophils corresponds to the severity of asthmatic reaction. Eosinophilia in mice models are shown to be associated with high interleukin-5 levels. Furthermore, mucosal bronchial biopsies conducted on patients with diseases such as asthma have been found to have higher levels of interleukin-5 leading to higher levels of eosinophils. The infiltration of eosinophils at these high concentrations causes an inflammatory reaction. This ultimately leads to airway remodelling and difficulty of breathing.

Eosinophils can also cause tissue damage in the lungs of asthmatic patients. High concentrations of eosinophil major basic protein and eosinophil-derived neurotoxin that approach cytotoxic levels are observed at degranulation sites in the lungs as well as in the asthmatic sputum.