Neutrophils are the most abundant white blood cell in blood and play a critical role in providing innate immunity against various offending agents. Agranulocytosis, also known as agranulosis or granulopenia, is an acute condition involving severe and dangerous neutropenia. Agranulocytosis is a condition in which the absolute neutrophil count (ANC) is less than 100 neutrophils per microlitre of blood. People with this condition are at a very high risk of severe infection. Broadly, it can be due to hereditary disease due to genetic mutation or acquired disease. Agranulocytosis can have various presentations, including fever, chills, sore throat, etc. It can be a life-threatening condition that requires prompt diagnosis and treatment.
Agranulocytosis can be broadly classified into two distinct categories, inherited and acquired. The hereditary disease is due to genetic mutations in the gene coding for neutrophils elastase or ELA2. The most commonly seen mutations are intronic substitutions that inactivate a splice site in intron 4. Acquired diseases may be due to various medications, chemicals, autoimmune conditions, and infections.
The following are the medications commonly involved with agranulocytosis:
Infections that can cause agranulocytosis include:
Autoimmune conditions such as lupus, rheumatoid arthritis, and bone marrow diseases like myelodysplastic and leukemias are also associated with agranulocytosis.
Agranulocytosis is a rare condition and occurs in all age groups, with a reported incidence ranging from 6 to 8 cases per million population per year. About 70% of the cases are found to be involved with medication usage. It also occurs more frequently in women than in men, either because of increased medication usage in females or due to increased incidence of autoimmune diseases in females. Agranulocytosis has no racial predilection.
Two main mechanisms responsible for agranulocytosis include inadequate or ineffective granulopoiesis and accelerated removal or destruction of neutrophils. Inadequate or ineffective granulopoiesis is due to generalized marrow failure. It also occurs in aplastic anemia, varieties of leukemias, myelodysplastic syndromes. Accelerated removal or destruction of neutrophils occurs due to immune-mediated injury to neutrophils or is idiopathic.
Marrow hypercellularity is seen when it results from excessive destruction of the mature neutrophils or ineffective granulopoiesis. In contrast, drugs that suppress granulocytopoiesis are associated with a marked decrease in mature granulocytic precursors in the marrow.
A history of a new medication used or a change in medication, recent exposure to chemical or physical agents, or recent viral or bacterial infection is usually associated with agranulocytosis. History of autoimmune disease or a strong family history of recurrent infection usually beginning from early childhood may be present. The initial symptoms are often malaise, fever, and chills, or infections, which usually present in the form of ulcers, necrotizing lesions of the gingiva, the floor of the mouth, buccal mucosa, pharynx, or other sites within the oral cavity. Pharyngitis, with difficulty in swallowing and multiple skin abscesses, could be another presentation of the disease. As the onset of agranulocytosis can be abrupt, sepsis can be the presentation. On examination, a fever usually > 40C, tachycardia, tachypnea, and hypotension are usually present.
The diagnosis of agranulocytosis requires a high degree of suspicion based on signs and symptoms, medication use, recent exposure to chemical agents, and infections. A complete blood count (CBC) with the differential count is used in the initial workup. An absolute neutrophil count (ANC) of less than 100 neutrophils per microlitre of blood is necessary to diagnose the condition. The peripheral blood smear should assess neutrophil morphology. A Wright-stained peripheral smear will show a marked decrease and absence of neutrophils. Erythrocyte sedimentation rate (ESR), C reactive protein (CRP), coagulation studies (prothrombin time, partial thromboplastin time, D-dimer), lactate dehydrogenase (LDH), antinuclear antibody (ANA), rheumatoid factor (RF), liver function tests (LFT), renal function tests (RFT), and urine analysis can be used in patients with relevant history. If the patient is febrile, cultures of the blood, urine, sputum, and other suspected sites of infection should be taken. No imaging technique is used to diagnose agranulocytosis, but chest X-ray (CXR) can be used for initial workup. Further, bone marrow aspiration and biopsy can be used after initial abnormal blood smear.
Agranulocytosis is a serious condition, and prompt treatment for it should be initiated. Once agranulocytosis is documented, any suspected offending medications or agents should be removed regardless of whether the patient is symptomatic or not. If it is due to drugs or offending agents, it usually resolves after one to three weeks after the offending agent is stopped. Meanwhile, general care like oral hygiene to prevent infection of the mucosa and teeth, control of oral and gingival lesion pain with anesthetic gel, and gargles are helpful. Stool softeners can be used in case of constipation. Skin infection and abrasion should be treated promptly.
Hematopoietic growth factors are used to accelerate the production, maturation, migration, and cytotoxicity of the neutrophils. Filgrastim, a granulocyte colony-stimulating factor (G-CSF), sargramostim, a granulocyte-macrophage colony-stimulating factor, pegfilgrastim (a long-acting filgrastim) are the agents used to treat agranulocytosis.
In case of infection, start specific antibiotic therapy with third-generation cephalosporins or equivalent. Cefepime, carbapenems, (e.g., meropenem, imipenem-cilastatin), or piperacillin-tazobactam can be used. In suspected cases of resistant bacteria, vancomycin or linezolid can be used in methicillin-resistant Staphylococcus aureus (MRSA). Linezolid or daptomycin can be used in cases of vancomycin-resistant enterococcus. Carbapenems can be used in the case of extended-spectrum beta-lactamase (ESBL) producing gram-negative bacteria. If the patient’s fever does not respond within 4-5 days or if the fever recurs with the administration of broad-spectrum antibiotics after an initial afebrile interval, consider adding empiric antifungal coverage with amphotericin B (preferably lipid formulation), a broad-spectrum azole (e.g., voriconazole), or an echinocandin (e.g., caspofungin).
Agranulocytosis should be differentiated from other conditions that cause bone marrow failure and leukemias. The following are the differential diagnosis of agranulocytosis:
A number of adverse prognostic factors are associated with the patient with agranulocytosis. These include:
The main complication of agranulocytosis is infection. The duration and severity of agranulocytosis directly correlate with the incidence of infection. When the ANC remains lower than 100 cells per microlitre of blood for longer than 3-4 weeks, the incidence of infection approaches 100%.
Sepsis is another major complication of agranulocytosis. Sepsis is a clinical syndrome due to the dysregulated bodily response to infection. As the number of mature granulocytes is severely decreased in agranulocytosis, the body is no longer able to fight the offending agents leading to sepsis, bacteremia, and septic shock. Septic shock is a type of distributive or vasodilatory shock that leads to circulatory and metabolic abnormalities and is associated with a higher rate of mortality.
Patients starting a new drug or a change in medication that has the propensity of causing agranulocytosis should be informed about the potential adverse effect of the medicine. They should be educated about the importance of frequent CBC testing in the initial period of drug use. With the drop of ANC below the cut-off value, the offending agent must be identified and stopped irrespective of the clinical signs and symptoms of agranulocytosis. Patients are also required to avoid contact with the people with respiratory tract infections, avoid going to crowded places, and asked to take proper precautions like a face mask and hand sanitizer whenever exposed to a crowded environment.
Agranulocytosis is a rare condition that may be asymptomatic or present with nonspecific symptoms and requires the efforts of an interprofessional team. In those patients taking new drugs or a change in their medications or undergoing cancer chemotherapy, clinicians should consider the possibility of agranulocytosis, especially when the patient has a fever or any clinical signs and symptoms of infection. The management involves interprofessional care that includes a hospitalist, intensivist, and pharmacist.
The patient monitoring is usually done by the nurses who should be aware of the condition and its presentation. The pharmacist should ensure that the patient is on the appropriate antibiotics in cases associated with sepsis. Also, the pharmacist must ensure that the patient has stopped using the offending agent. Close communication between the interprofessional team is vital to improving patient outcomes.
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