Neutropenia is usually detected shortly after birth, affecting 6% to 8% of all newborns in neonatal intensive care units (NICUs). Out of the approximately 600,000 neonates annually treated in NICUs in the United States, 48,000 may be diagnosed as neutropenic. The incidence of neutropenia is greater in premature infants. Six to fifty-eight percent of preterm neonates are diagnosed with this auto-immune disease. The incidence of neutropenia correlates with decreasing birth weight. The disorder is seen up to 38% in infants that weigh less than 1000g, 13% in infants weighing less than 2500g, and 3% of term infants weighing more than 2500 g. Neutropenia is often temporary, affecting most newborns in only first few days after birth. In others, it becomes more severe and chronic indicating a deficiency in innate immunity.

The pathophysiology of neutropenia can be divided into "congenital" and "acquired". In congenital neutropenia (cyclic neutropenia) is autosomal dominant, mutations in the ELA2 gene (neutrophil elastase), is the genetic reason for this condition.

Acquired neutropenia (immune-associated neutropenia) is due to anti-neutrophil antibodies that work against neutrophil-specific antigens, ultimately altering neutrophil function.

Neutropenia fever can complicate the treatment of cancers. Observations of pediatric patients have noted that fungal infections are more likely to develop in patients with neutropenia. Mortality increases during cancer treatments if neutropenia is also present.

Congenital neutropenia is determined by blood neutrophil counts (absolute neutrophil counts or ANC) < 0.5 × 10/L and recurrent bacterial infections beginning very early in childhood.

Congenital neutropenia is related to alloimmunization, sepsis, maternal hypertension, twin-to-twin transfusion syndrome, and Rh hemolytic disease.

A large number of drugs

have been associated with agranulocytosis, including antiepileptics (such as carbamazepine and valproate), antithyroid drugs (carbimazole, methimazole, and propylthiouracil), antibiotics (penicillin, chloramphenicol and co-trimoxazole), ACE inhibitors (benazepril), cytotoxic drugs, gold, NSAIDs (indomethacin, naproxen, phenylbutazone, metamizole), mebendazole, allopurinol the antidepressants mianserin and mirtazapine, and some antipsychotics (the atypical antipsychotic clozapine in particular). Clozapine users in the United States, Australia, Canada, and the UK must be nationally registered for monitoring of low WBC and absolute neutrophil counts (ANC).

Although the reaction is generally idiosyncratic rather than proportional, experts recommend that patients using these drugs be told about the symptoms of agranulocytosis-related infection, such as a sore throat and a fever.

The Centers for Disease Control traced outbreaks of agranulocytosis among cocaine users, in the US and Canada between March 2008 and November 2009, to the presence of levamisole in the drug supply. The Drug Enforcement Administration reported that, as of February 2010, 71% of seized cocaine lots coming into the US contained levamisole as a cutting agent. Levamisole is an antihelminthic (i.e. deworming) drug used in animals. The reason for adding levamisole to cocaine is unknown, although it can be due to their similar melting points and solubilities.

Certain medications can alter the number and function of white blood cells.

Medications that can cause leukopenia include clozapine, an antipsychotic medication with a rare adverse effect leading to the total absence of all granulocytes (neutrophils, basophils, eosinophils). The antidepressant and smoking addiction treatment drug bupropion HCl (Wellbutrin) can also cause leukopenia with long-term use. Minocycline, a commonly prescribed antibiotic, is another drug known to cause leukopenia. There are also reports of leukopenia caused by divalproex sodium or valproic acid (Depakote), a drug used for epilepsy (seizures), mania (with bipolar disorder) and migraine.

The anticonvulsant drug, lamotrigine, has been associated with a decrease in white blood cell count.

The FDA monograph for metronidazole states that this medication can also cause leukopenia, and the prescriber information suggests a complete blood count, including differential cell count, before and after, in particular, high-dose therapy.

Immunosuppressive drugs, such as sirolimus, mycophenolate mofetil, tacrolimus, ciclosporin, leflunomide and TNF inhibitors, have leukopenia as a known complication. Interferons used to treat multiple sclerosis, such as interferon beta-1a and interferon beta-1b, can also cause leukopenia.

Chemotherapy targets cells that grow rapidly, such as tumors, but can also affect white blood cells, because they are characterized by bone marrow as rapid growing. A common side effect of cancer treatment is neutropenia, the lowering of neutrophils (a specific type of white blood cell).

Decreased white blood cell count may be present in cases of arsenic toxicity.

Autoimmune neutropenia is a form of neutropenia which is most common in infants and young children where the body identifies the neutrophils as enemies and makes antibody to destroy them.

Primary autoimmune neutropenia (AIN) is an autoimmune disease first reported in 1975 that primarily occurs in infancy. In autoimmune neutropenia, the immune system produces autoantibodies directed against the neutrophilic protein antigens in white blood cells known as granulocytic neutrophils (granulocytes, segmented neutrophils, segs, polysegmented neutrophils, polys). These antibodies destroy granulocytic neutrophils. Consequently, patients with autoimmune neutropenia have low levels of granulocytic neutrophilic white blood cells causing a condition of neutropenia. Neutropenia causes an increased risk of infection from organisms that the body could normally fight easily.

Who is Affected?

Primary autoimmune neutropenia has been reported as early as the second month of life although most cases are diagnosed in children between 5 and 15 months of age. Girls have a slightly higher risk of developing AIN than boys. In neutropenia discovered at birth or shortly after birth, a diagnosis of allo-immune neutropenia (from maternal white blood cell antibodies passively transferred to the infant) is more likely.

Neutropenia

In infants neutropenia is defined by absolute neutrophil counts less than 1000/uL. After the first year of life neutropenia is defined by absolute counts less than 1500/uL. Neutropenia may be primary in which it is the only blood abnormality seen. In secondary neutropenia, other primary conditions occur, including other autoimmune diseases, infections, and malignancies. Neutropenia is considered chronic when it persists for more than 6 months.

Symptoms and Disease Course

Neutropenia, which may be discovered on routine blood tests, typically causes benign infections even when the condition is severe. Ear infections (otitis media) are the most common infection seen in autoimmune neutropenia and typically infection responds to antibiotic treatment alone. Infections associated with primary AIN are usually mild and limited, including skin infections such as impetigo, gastroenteritis, upper respiratory tract infections, and ear infections. Rarely, cellulitis and abscesses may occur.

Studies of children studied for up to six years showed that most cases of autoimmune neutropenia resolved spontaneously after a median of 17 months. In 80 percent of patients, neutropenia persisted for 7 to 24 months.

Diagnosis

Patients with autoimmune neutropenia are diagnosed on the basis of blood tests showing neutropenia and the presence of granulocyte-specific antibodies. In some cases, tests for granulocyte-specific antibodies need to be repeated several times before a positive result is seen. Bone marrow aspiration, if performed, is typically normal or it can show increased cell production with a variably diminished number of segmented granulocytes.

s association with prior parvovirus B19 has been made, but this hasn’t been confirmed. Similar to the platelet deficiency idiopathic thrombocytopenic purpura, vaccines are suspected of triggering this disorder.

Treatment

Treatment consists of corticosteroids to reduce autoantibody production, antibiotics to prevent infection and granulocyte colony-stimulating factor (G-CSF) to temporarily increase neutrophil counts. In cases of severe infection or the need for surgery, intravenous immunoglobulin therapy may be used.

This form usually lessens in severity within two years of diagnosis.

The use of prophylactic antibiotics has been proposed.

See article at BioMed Central site:

Agranulocytosis may be asymptomatic, or may clinically present with sudden fever, rigors and sore throat. Infection of any organ may be rapidly progressive (e.g., pneumonia, urinary tract infection). Septicemia may also progress rapidly.

Low white cell count may be due to acute viral infections, such as a cold or influenza. It has been associated with chemotherapy, radiation therapy, myelofibrosis, aplastic anemia (failure of white cell, red cell and platelet production), stem cell transplant, bone marrow transplant, HIV, AIDS, and steroid use.

Other causes of low white blood cell count include systemic lupus erythematosus, Hodgkin's lymphoma, some types of cancer, typhoid, malaria, tuberculosis, dengue, rickettsial infections, enlargement of the spleen, folate deficiencies, psittacosis, sepsis, Sjögren's syndrome and Lyme disease. It has also been shown to be caused by deficiency in certain minerals, such as copper and zinc.

Pseudoleukopenia can develop upon the onset of infection. The leukocytes (predominately neutrophils, responding to injury first) start migrating toward the site of infection, where they can be scanned. Their migration causes bone marrow to produce more WBCs to combat infection as well as to restore the leukocytes in circulation, but as the blood sample is taken upon the onset of infection, it contains low amount of WBCs, which is why it is termed "pseudoleukopenia".

Bone marrow suppression due to azathioprine can be treated by changing to another medication such as mycophenolate mofetil (for organ transplants) or other disease-modifying drugs in rheumatoid arthritis or Crohn's disease.

Leukocytosis is very common in acutely ill patients. It occurs in response to a wide variety of conditions, including viral, bacterial, fungal, or parasitic infection, cancer, hemorrhage, and exposure to certain medications or chemicals including steroids.

For lung diseases such as pneumonia and tuberculosis, WBC count is very important for the diagnosis of the disease, as leukocytosis is usually present.

The mechanism that causes leukocytosis can be of several forms: an increased release of leukocytes from bone marrow storage pools, decreased margination of leukocytes onto vessel walls, decreased extravasation of leukocytes from the vessels into tissues, or an increase in number of precursor cells in the marrow.

Certain medications, including corticosteroids, lithium and beta agonists, may cause leukocytosis.

Monocytopenia is a form of leukopenia associated with a deficiency of monocytes. The causes of monocytopenia include: acute infections, stress, treatment with glucocorticoids, aplastic anemia, hairy cell leukemia, acute myeloid leukemia, treatment with myelotoxic drugs and genetic syndromes, as for example MonoMAC syndrome.

It has been proposed as a measure to predict neutropenia, though some research indicates that it is less effective than lymphopenia.

Below are blood reference ranges for various types leucocytes/WBCs. The 97.5 percentile (right limits in intervals in image, showing 95% prediction intervals) is a common limit for defining leukocytosis.

Myelokathexis is a congenital disorder of the white blood cells that causes severe, chronic leukopenia (a reduction of circulating white blood cells) and neutropenia (a reduction of neutrophil granulocytes). The disorder is believed to be inherited in an autosomal dominant manner. Myelokathexis refers to retention (kathexis) of neutrophils in the bone marrow (myelo). The disorder shows prominent neutrophil morphologic abnormalities.

Myelokathexis is amongst the diseases treated with bone marrow transplantation and cord blood stem cells.

WHIM syndrome is a very rare variant of severe congenital neutropenia that presents with warts, hypogammaglobunemia, infections, and myelokathexis. A gain in function mutation resulting in a truncated form of CXCR4 is believe to be its cause.

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

Eosinophilia can be idiopathic (primary) or, more commonly, secondary to another disease. In the Western World, allergic or atopic diseases are the most common causes, especially those of the respiratory or integumentary systems. In the developing world, parasites are the most common cause. A parasitic infection of nearly any bodily tissue can cause eosinophilia.

Diseases that feature eosinophilia as a sign include:

- Allergic disorders

- Asthma

- Hay fever

- Drug allergies

- Allergic skin diseases

- Pemphigus

- Dermatitis herpetiformis

- IgG4-related disease

- Parasitic infections

- Addison's disease and stress-induced suppression of adrenal gland function

- Some forms of malignancy

- Acute lymphoblastic leukemia

- Chronic myelogenous leukemia

- Eosinophilic leukemia

- Clonal eosinophilia

- Hodgkin lymphoma

- Some forms of non-Hodgkin lymphoma

- Lymphocyte-variant hypereosinophilia

- Systemic mastocytosis

- Systemic autoimmune diseases

- Systemic lupus erythematosus

- Kimura disease

- Eosinophilic granulomatosis with polyangiitis

- Eosinophilic fasciitis

- Eosinophilic myositis

- Eosinophilic esophagitis

- Eosinophilic gastroenteritis

- Cholesterol embolism (transiently)

- Coccidioidomycosis (Valley fever), a fungal disease prominent in the US Southwest.

- Human immunodeficiency virus infection

- Interstitial nephropathy

- Hyperimmunoglobulin E syndrome, an immune disorder characterized by high levels of serum IgE

- Idiopathic hypereosinophilic syndrome.

- Congenital disorders

- Hyperimmunoglobulin E syndrome

- Omenn syndrome

- Familial eosinophilia

In developing new chemotherapeutics（化疗方法），the efficacy of the drug against the disease is often balanced against the likely level of myelotoxicity the drug will cause. In-vitro colony forming cell (CFC) assays using normal human bone marrow grown in appropriate semi-solid media such as ColonyGEL have been shown to be useful in predicting the level of clinical myelotoxicity a certain compound might cause if administered to humans. These predictive in-vitro assays reveal effects the administered compounds have on the bone marrow progenitor cells that produce the various mature cells in the blood and can be used to test the effects of single drugs or the effects of drugs administered in combination with others.

Helminths are common causes of hypereosiophilia and eosinophilia in areas endemic to these parasites. Helminths infections causing increased blood eosinophil counts include: 1) nematodes, (i.e. "Angiostrongylus cantonensis" and Hookworm infections), ascariasis, strongyloidiasis trichinosis, visceral larva migrans, Gnathostomiasis, cysticercosis, and echinococcosis; 2) filarioidea, i.e. tropical pulmonary eosinophilia, loiasis, and onchocerciasis; and 3) flukes, i.e. shistosomiasis, fascioliasis, clonorchiasis, paragonimiasis, and fasciolopsiasis. Other infections associated with increased eosinophil blood counts include: protozoan infections, i.e. "Isospora belli" and "Dientamoeba fragilis") and sarcocystis); fungal infections (i.e. disseminated histoplasmosis, cryptococcosis especially in cases with [[central nervous system]] involvement), and coccidioides); and viral infections, i.e. Human T-lymphotropic virus 1 and HIV.

Hypereosiophilia or eosinophilia may be associated with the following autoimmune diseases: systemic lupus erythematosus eosinophilic fasciitis, eosinophilic granulomatosis with polyangiitis, dermatomyositis, severe rheumatoid arthritis, progressive systemic sclerosis, Sjogren syndrome, thromboangiitis obliterans, Behcet syndrome, IgG4-related disease, inflammatory bowel diseases, sarcoidosis, bullous pemphigoid, and dermatitis herpetiformis.

In cardiovascular disease, increased white blood cell counts have been shown to indicate a worse prognosis.

Febrile neutropenia can develop in any form of neutropenia, but is most generally recognized as a complication of chemotherapy when it is myelosuppressive (suppresses the bone marrow from producing blood cells).

An increase in eosinophil granulocyte is known as eosinophilia.

Granulocytosis can be a feature of a number of diseases:

- Infection, especially bacterial

- Malignancy, most notably leukemia (it is the main feature of chronic myelogenous leukemia, CML)

- Autoimmune disease

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.

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.

The Multinational Association for Supportive Care in Cancer (MASCC) risk index can be used to identify low-risk patients (score ≥21 points) for serious complications of febrile neutropenia (including death, intensive care unit admission, confusion, cardiac complications, respiratory failure, renal failure, hypotension, bleeding, and other serious medical complications). The score was developed to select patients for therapeutic strategies that could potentially be more convenient or cost-effective. A prospective trial demonstrated that a modified MASCC score can identify patients with febrile neutropenia at low risk of complications, as well.

In contrast, the Clinical Index of Stable Febrile Neutropenia (CISNE) score is specific of patients with solid tumors and seemingly stable episodes. CISNE is able to discriminate groups of patients who are at low, intermediate, and high risk of complications in this population. With the CISNE, the complication rate was determined to be 1.1% for low-risk patients, 6.2% for intermediate-risk patients, and 36.0% for high-risk patients. The prime purpose of this model was to avoid complications from an early hospital release. On the contrary, CISNE should not be used so much to select low-risk patients for outpatient treatment.

Cytopenia is a reduction in the number of mature blood cells. It takes a number of forms:

- Low red blood cell count: resulting in anemia.

- Low white blood cell count: leukopenia or neutropenia. Because neutrophils make up at least half of all white cells, they are almost always low in leukopenia .

- Low platelet count: thrombocytopenia.

- Low granulocyte count: granulocytopenia

- Low red blood cell, white blood cell, and platelet counts: pancytopenia.