Neutropenia overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:
Overview
Neutropenia is a hematological disorder characterized by an abnormally low number of neutrophil granulocytes (a type of white blood cell). Neutrophils usually make up 50-70% of circulating white blood cells and serve as the primary defense against infections by destroying bacteria in the blood. Hence, patients with neutropenia are more susceptible to bacterial infections and without prompt medical attention, the condition may become life-threatening. Neutropenia can be acute or chronic depending on the duration of the illness. A patient has chronic neutropenia if the condition lasts for greater than 3 months. It is sometimes used interchangeably with the term leukopenia. However, neutropenia is more properly considered a subset of leukopenia as a whole. Some patients, such as those with constitutional/benign ethnic neutropenia, suffer relatively few complications, however neutropenia related to cytotoxic chemotherapy, hematopoietic stem cell transplant, or other causes of bone marrow suppression may present as a medical emergency.
Classification
Calculated based on blood count differential, neutropenia is defined as an absolute neutrophil count (ANC) less than 1,500 cells per microliter and is calculated by multiplying the total white blood cell (WBC) count by the percentage of neutrophils (including both mature neutrophils and band forms).
- Mild Neutropenia: ANC 1,000-1500 cells/microliter
- Moderate Neutropenia: ANC 500-1000 cells/microliter
- Severe Neutropenia (Agranulocytosis): ANC <500 cells/microliter
NOTE: These ranges are based on Caucasian patients, whereas African Americans and some ethnicities have mild neutropenia without increased risk of complications. Neutropenia in African American individuals is defined as an ANC < 1200 cells/microliter. This often overlooked fact results in overdiagnosis of neutropenia in African American population.[1]
Severe chronic neutropenia may be present at birth (congenital neutropenia) or may occur at any stage in life (acquired neutropenia). There are several types of severe chronic neutropenia:
Severe congenital neutropenia — a rare inherited form of the disease usually detected soon after birth. It affects children mainly and may result in premature loss of teeth and peremptory gum infections. The most severe form of chronic congenital neutropenia is known as Kostmann’s syndrome. It is genetically heterogeneous. Most commonly, it arises as a result of new,autosomal dominant mutations in the gene, ELA2, encoding the neutrophil granule protease, neutrophil elastase, NE. The gene responsible for many cases of autosomal recessively inherited severe congenital neutropenia is HAX1. The mechanism for congenital neutropenia is not well-understood. There is evidence that mutations in neutrophil elastase, or in other genes associated with syndromic forms of neutropenia, disrupt its intracellular trafficking. Apoptosis may be a final effector for neutropenia, but the original studies from Dale and Aprikian supporting this pathway were retracted.
Cyclic neutropenia — tends to occur every three weeks and lasting three to six days at a time due to changing rates of cell production by the bone marrow. It is often present among several members of the same family. Cyclic neutropenia is also the result of autosomal dominantly inherited mutations in ELA2, the gene encoding neutrophil elastase.
Idiopathic neutropenia — a rare form of neutropenia which develops in children and adults usually in response to an illness. It is diagnosed when the disorder cannot be attributed to any other diseases and often causes life-threatening infections.
Myelokathexis — a rare form of inherited autosomal dominant disease associated with severe neutropenia. Some but not all patients have warts, Hypogammaglobulinemia, and recurrent Infections. Therefore myelokathexis is also known as the W.H.I.M. syndrome. In spite of severe neutropenia (low number of neutrophils) in peripheral blood of myelokathexis patients, their bone marrow is hypercellular and it is packed with mature neutrophils indicating an impaired mobilization of hematopoietic cells in this disorder. Truncating mutations in the human cytokine receptor CXCR4 gene were identified in most of the families afflicted by myelokathexis. The molecular mechanism is not yet defined. Recent reports demonstrate that CXCR4 mutations appear to result in an increased sensitivity of bone marrow hematopoietic cells to its ligand, a stromal-derived growth factor SDF-1 that provides proliferative and survival signals.
Autoimmune neutropenia — most common in infants and young children where the body identifies the neutrophils as enemies and makesantibody to destroy them. This form usually lessens in severity within two years of diagnosis.
Drug-induced neutropenia — Many drugs can cause agranulocytosis (complete absence of white cells) and neutropenia. Manyanti-neoplastic drugs cause agranulocytosis and neutropenia by bone marrow suppression. Neutropenia and agranulocytosis can also result from antibody or complement-mediated damage to the stem cells. Some drugs may cause increased peripheral destruction of white cells. About 75% of all cases of agranulocytosis in the United States are related to medication. Clozapine, File:Example.jpgprocainamide, anti-thyroid drugs (e.g. methimazole, and sulfasalazine are at the top of the list of drugs causing this problem, but many others (such as antiepileptics) have been implicated.
Pathophysiology
Neutropenia develops as a result of one of the three following mechanisms:
1) Impaired granulocyte production
- Hematologic malignancy with bone marrow infiltration
- Myelosuppressive chemotherapy or other medications that are toxic to the bone marrow
- Nutritional deficiencies
2) Margination (process where free flowing blood cells exit circulation)
- Splenic sequestration
- Adherence to the vascular endothelium
3) Peripheral destruction
- Autoimmune hemolysis
- Drug-induced hemolysis
Causes
The most common etiologies are constitutional or benign ethnic neutropenia (BEN) and drug-induced neutropenia.
BEN is more often seen in blacks, Yemenites, West Indians, and Arab Jordanians with up to 4.5% prevalence in these populations [1]. In these individuals, a mutation in the Duffy antigen gene - a gene which encodes a red blood cell receptor used by malaria to enter these cells - both confers a protective effect against this parasite and, for unclear reasons, lowers the circulating neutrophil count. While quite common, the neutropenia is typically mild (ANC 1,000-1500 cells/microliter) and does not predispose to increased risk of infection or increased risk of febrile neutropenia in the setting of chemotherapy as these individuals have normal bone marrow neutrophil reserves [2] [3] [4].
Malignancy is often associated with neutropenia, due to impaired production from myelodysplastic syndromes and hematological malignancies with bone marrow infiltration, hemolysis and impaired production from cytotoxic chemotherapy, and antibody-mediated destruction of neutrophils.
Alternative etiologies include post-infectious neutropenia resulting from bacterial, fungal, or viral infections. While bacterial infections typically cause leukocytosis, Salmonella and Shigella enteritis, brucellosis, tularemia, tuberculosis, and rickettsial diseases such as Rocky Mountain Spotted Fever (RMSF) can present with neutropenia. Parasitic diseases with neutropenia include Leishmaniasis with hemolysis and splenic sequestration and malaria due to hyper-reactive malarial splenomegaly (HMS). Viral etiologies include HIV, EBV, CMV, HHV-6, viral hepatitis, dengue, yellow fever, and common childhood exanthematous viruses including measles, varicella, and rubella where ANC nadirs around the time of the onset of rash.
Immunodeficiencies are frequently associated with neutropenia (38% in Hyper IgM syndrome, 12% in CVID, and 7% in X-linked agammaglobulinemia) as are autoimmune disorders including up to 50% of patients with systemic lupus erythematosus, yet with lower overall prevalence. While rheumatoid arthritis infrequently presents with neutropenia, severe neutropenia can develop in the setting of large granular lymphocyte (LGL) leukemia or Felty syndrome [5].
Finally, nutritional deficiencies resulting in neutropenia are typically attributed to vitamin B12, folate, and copper and are related to inadequate dietary intake, pernicious anemia, bariatric surgery, and malabsorptive syndromes.
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
Common Causes
- Aplastic anemia
- Cancer
- Cytotoxic chemotherapy
- Hemodialysis
- Medications
- Radiation therapy
- Vitamin deficiencies e.g. folate, Vitamin B12
Causes by Organ System
Causes in Alphabetical Order
Epidemiology and Demographics
Neutropenia is typically identified in at-risk patients undergoing cytotoxic chemotherapy or on other myelosuppressive medications. As noted above, some ethnicities have an unusually high prevalence of incidentally identified mild neutropenia, also termed constitutional or benign ethnic neutropenia (BEN). This is most common in blacks, Yemenites, West Indians, and Arab Jordanians and is suggested to be caused by a mutation in the Duffy antigen on red blood cells that helps to confer resistance to malaria. As the name suggests, these cases are typically mild and do not result in immunosuppression.
History and Symptoms
Neutropenia can go undetected until the patient develops secondary, and often severe, infections or sepsis. Some common infections can take an unexpected course in neutropenic patients; formation of pus, for example, can be notably absent, as this requires circulating neutrophil granulocytes. History should focus on symptoms suggestive of malignancy or infections, patient or family history of autoimmune or immunodeficiency disorders, risk factors for infections including HIV and hepatitis, and any unusual dietary practices or history of bariatric surgery. Medications should be reviewed with particular attention to chemotherapeutics, antibiotics, antiepileptics, and psychoactive drugs as well as documenting any new medications started within the preceding few months.
Common presenting symptoms in neutropenic patients include:
- Fever
- Frequent infections due to lessened ability to fight bacterial infections
- Mouth ulcers
- Diarrhea
- Burning sensation when urinating
- Unusual redness, pain, or swelling around a wound
- Sore throat
- Shortness of breath
- Shaking chills
Physical Examination
A rectal examination should not be performed in a patient with neutropenia.
Medical Therapy
There is no specific therapy for neutropenia itself aside from removing the offending agents in drug-induced cases and treating the underlying disease in other, however recombinant G-CSF (granulocyte-colony stimulating factor) can be considered to speed myeloid reconstitution.
Asymptomatic, mild to moderate neutropenia can often be monitored closely on an outpatient basis with serial CBCs and evaluation for medications, infections, or alternative sources of neutropenia as described in detail above. Offending medications are often held and the patient is monitored for response to discontinuation while evaluating for alternative, more concerning etiologies. With mild neutropenia, medications can often be reintroduced after neutrophil counts recover as the neutropenia is typically dose-dependent.
Patients who are febrile, acutely ill, or with severe neutropenia often warrant urgent hospitalization for close monitoring and treatment. Offending medications must be discontinued as drug-induced agranulocytosis presents up to a 10% mortality and is very likely to recur if the offending agent is restarted.
Resuscitate all patients screening positive for sepsis syndromes per goal-directed therapy and the surviving sepsis campaign. Initiate empiric antibiotics as early as possible after cultures are drawn and within 60 minutes of presentation as there is significantly higher mortality when antibiotic administration is delayed [6] [7] [8]. Initial antibiotic selection should provide broad coverage of the most common, most virulent, and most likely pathogens and should be bactericidal so as not to rely on assistance from the host's impaired immune system. Remove central venous catheters when possible if there is suspicion for infection or with positive blood cultures.
Low risk patients
ANC>100 cells/microliter, normal liver and renal function, normal chest x-ray, no evidence of central line infection, MASCC >21, and duration of neutropenia expected <7 days in a patient with close monitoring and access to medical care.
- Ciprofloxacin 500mg PO BID + amoxicillin/clavulanate 500mg PO TID
High risk patients
Hospitalize and initiate empiric parenteral antimicrobial therapy. IDSA guidelines recommend initial monotherapy with:
- Cefepime 2 g IV Q8H
- Meropenem 1 g IV Q8H
- Imipenem/cilastatin 500 mg IV Q6H
- Piperacillin/tazobactam 4.5 g IV Q6H
- Ceftazidime 2 g IV Q8H (recent data shows increasing resistance to ceftazidime and inferior Gram-positive coverage to alternative regimens)
Indications for resistant Gram-positive coverage
Vancomycin or linezolid is NOT recommended as part of initial treatment unless one of the following is present and, if started, should be discontinued after 2-3 days if there is no evidence of Gram-positive infection:
- Hemodynamic instability
- Suspected catheter-associated infection
- Mucositis or cellulitis
- History of MRSA infection or colonization
- Gram-positive bacteremia prior to final culture results
- Recent fluoroquinolone prophylaxis
Alternative regimens
- Pneumonia: Broaden coverage to include Vancomycin or Linezolid and a macrolide or fluoroquinolone. Consider PJP.
- Diarrhea: Evaluate for C.difficile, treat if positive.
- Sinusitis: Urgent ENT evaluation. Broaden coverage to include invasive fungi.
- Oral ulceration: Consider broadening coverage to include Acyclovir for HSV and/or Fluconazole for Candida.
- BMT: Evaluate for CMV. Consider broadening coverage to include Ganciclovir.
- Hemodynamic instability: Broaden coverage to include resistant Gram-positive, Gram-negative, and anaerobic bacteria and fungi, typically with Vancomycin or Linezolid, a Carbapenem, and Amphotericin, Voriconazole, or Caspofungin.
Persistent Fever
Continue empiric therapy until either culture data is available to direct management or after 3-5 days if the patient fails to improve. The median time to defercescence in adequately treated patients is 5 days with hematologic malignancies and 2-3 days with solid tumors. If the patient is still febrile or develops recurrent fevers after this time period further work up is suggested.
Re-evaluate sources of infection. Re-evaluate indications for resistant Gram-positive coverage and consider adding vancomycin or linezolid. Re-evaluate indications for resistant Gram-negative organisms and anaerobes and consider broadening to carbapenem antibiotics. Consider fungal coverage in high risk patients if fevers persist after 4-7 days of appropriate antibiotic coverage and duration of neutropenia is expected to last >7 days as follows:
- Caspofungin 70 mg IV x 1 dose, then 50mg IV daily
- Liposomal Amphotericin B 3 mg/kg/day
- Voriconazole 6 mg/kg IV Q12H x 2 doses, then 4 mg/kg IV Q12H
Caspofungin provides excellent coverage for Candida and is well tolerated, however nodular pulmonary infiltrates warrant coverage of Aspergillus with Voriconazole or Amphotericin B as echinocandins do not provide adequate coverage of Aspergillus or endemic fungi.
In cases of severe or refractory febrile neutropenia, consider granulocyte colony stimulating factor (G-CSF) to facilitate neutrophil count recovery, however routine use is NOT recommended as it does not reduce duration of fever or mortality despite shortening duration of neutropenia [9].
Duration of Antimicrobials
Documented infection: Continue antimicrobials as directed by culture data. Continue treatment for the standard duration for that particular infection and until myeloid recovery (ANC>500 cells/microliter). If counts recover prior to completing the treatment course, consider transition to an oral regimen guided by culture data.
Negative Cultures: Continue empiric antimicrobial regimen until myeloid recovery (ANC>500 cells/microliter). If afebrile with no evidence of ongoing infection, consider transition to oral regimen (e.g. Ciprofloxacin + Amoxicillin/Clavulanate) and continue until myeloid recovery.
References
- ↑ Hsieh MM, Everhart JE, Byrd-Holt DD, Tisdale JF, Rodgers GP (2007). "Prevalence of neutropenia in the U.S. population: age, sex, smoking status, and ethnic differences". Ann. Intern. Med. 146 (7): 486–92. PMID 17404350.
- ↑ Shoenfeld Y, Alkan ML, Asaly A, Carmeli Y, Katz M (1988). "Benign familial leukopenia and neutropenia in different ethnic groups". Eur J Haematol. 41 (3): 273–7. PMID 3181399.
- ↑ Shoenfeld Y, Ben-Tal O, Berliner S, Pinkhas J (1985). "The outcome of bacterial infection in subjects with benign familial leukopenia (BFL)". Biomed Pharmacother. 39 (1): 23–6. PMID 4027348.
- ↑ Hsieh MM, Tisdale JF, Rodgers GP, Young NS, Trimble EL, Little RF (2009). "Neutrophil count in African Americans: lowering the target cutoff to initiate or resume chemotherapy?". J Clin Oncol. 28 (10): 1633–7. PMID 20194862.
- ↑ Bucknall RC, Davis P, Bacon PA, Jones JV (2009). "Neutropenia in rheumatoid arthritis: studies on possible contributing factors". Ann Rheum Dis. 41 (3): 242–7. PMID 6979979.
- ↑ Schimpff S, Satterlee W, Young VM, Serpick A (1971). "Empiric therapy with carbenicillin and gentamicin for febrile patients with cancer and granulocytopenia". N Engl J Med. 284 (19): 1061–5. PMID 4994878.
- ↑ Kumar A, Roberts D, Wood KE, Light B, Parrillo JE, Sharma S, Suppes R, Feinstein D, Zanotti S, Taiberg L, Gurka D, Kumar A, Cheang M (2006). "Duration of hypotension before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock". Crit Care Med. 34 (6): 1589–96. PMID 16625125.
- ↑ Rosa RG, Goldani LZ. (2014). "Cohort study of the impact of time to antibiotic administration on mortality in patients with febrile neutropenia". Antimicrob Agents Chemother. 58 (7): 3799–803. PMID 24752269.
- ↑ Aapro MS; et al. (2011). "2010 update of EORTC guidelines for the use of granulocyte-colony stimulating factor to reduce the incidence of chemotherapy-induced febrile neutropenia in adult patients with lymphoproliferative disorders and solid tumors". Eur J Cancer. 47 (1): 8–32. PMID 21095116.