Introduction
Autoimmune neutropenia (AIN) is a clinical condition characterized by lowered count of neutrophils which can lead to defects in cell-mediated or humoral immunity. It belongs to heterogeneous disorder. It can present itself individually or can be associated with various other disorders related to the hematopoietic or blood system. As of now, there are no specific diagnostic tests available for this condition and this is diagnosed by exclusion method.
What Are The Types?
There are basically two major types of autoimmune neutropenia which are as follows:
1. Primary AIN: It is more commonly seen in children, especially between the age of six months to 12 months. The pathophysiology can be associated with antibodies against commonly presenting neutrophil antigens, like human neutrophil antigen 1 (HNA1), human neutrophil antigen 2 (HNA2), CD11b, and FCγRIIIb. This is a self-limiting condition wherein more than 95 % of the children recover with normal neutrophil counts within two years. The patients can be usually managed with antibiotic therapy and do not require further intervention.
2. Secondary AIN: It is more commonly observed in adults, and usually witnessed in the setting of systemic autoimmune diseases. The cause of this condition is heterogeneous in nature and the main aim of the treatment is to minimize the morbidity and mortality related to serious infections. Also, the focus is on achieving the management of the underlying autoimmune condition.
3. Drug-Induced Agranulocytosis: This is an acute type of immune neutropenia. It is an idiosyncratic immune response that is observed in patients with profound neutropenia.
What Are The Signs And Symptoms?
There can be various presentations of this condition which are listed below:
- Fever - If the absolute neutrophil count (ANC) is less than 500 and is associated with fever, it can be life-threatening. In such cases, the patient requires immediate hospitalization for evaluation and management with the use of broad-spectrum antibiotics.
- Thrombocytopenia or Hemolytic Anemia - If there is thrombocytopenia or hemolytic anemia in a patient with new-onset neutropenia, hematologic malignancy should be expected rather than a primary immune type. However, a combination of cytopenias can be there in the setting of autoimmune disease.
- Neutropenia or Decrease in Neutrophil Count - Neutropenia in a patient with unknown autoimmune disease is usually mild. It can be a representation of the underlying autoimmune condition rather than a hematologic disorder and thus, does not require any specific treatment.
- Splenomegaly - Splenomegaly means enlarged spleen. If this is observed in a patient with neutropenia associated with rheumatoid arthritis, Felty syndrome should be suspected.
- Agranulocytosis - Acute agranulocytosis most commonly occurs due to drug-induced and leads to neutropenia. All the drugs causing this condition should be stopped and required antibiotics should be started.
How Can It Be Diagnosed?
When you visit your physician, you will be asked questions related to your symptoms, personal history, and medical issues. Then physical examination was done and certain laboratory tests will be done for evaluation and confirmation of the diagnosis and treatment.
1. Complete Blood Count - Complete blood count (CBC) with differential counts of various cells is estimated. It is advisable to repeat this test at least twice, at two-week intervals and thus, it will help in confirmation of the diagnosis.
2. Folate and B12 count - Folate and B12 estimation will aid in ruling out neutropenia associated with nutritional deficiencies.
3. Bone Marrow Aspiration and Core Biopsy - Bone marrow examination helps in ruling out other causes of neutropenia like lymphoproliferative neoplasm, myelodysplastic syndrome, or leukemia. It is also advisable to include cytogenetics and flow cytometry in the evaluation.
4. Flow Cytometry - Flow cytometry can be done for large granular lymphocytes (LGL). LGL related neutropenia can be sporadic or can be related to autoimmune diseases like rheumatoid arthritis.
5. Antineutrophil Antibody Studies - This test is difficult to perform and rarely used.
What Are The Other Conditions Associated With Neutropenia?
1. Large Granular Lymphocyte Leukemia - It is a chronic lymphoproliferative disease that occurs due to the clonal proliferation of lymphocytes.
2. Rheumatoid Arthritis - Rheumatoid arthritis (RA) associated neutropenia can be severe and can be related to significant morbidity. The triad of RA, neutropenia, and splenomegaly is called “Felty syndrome”.
3. Systemic Lupus Erythematosus - Neutropenia is very commonly seen in patients diagnosed with systemic lupus erythematosus (SLE). However, neutropenia in these patients is less severe. Neutropenia that requires direct intervention is rarely seen. Also, complications related to an infection can affect the results of the immunosuppressive drugs that are used to treat SLE.
There are certain conditions when the patients might require some more aggressive tests to diagnose the condition. Patients with persistent neutropenia which occurs for more than 2 weeks to 4 weeks, or those having severe infections or fever accompanied with neutropenia, and patients with other hematological disorders should undergo such tests. This will help in diagnosing the condition and the required treatment plan can be finalized.
Some of the tests that should be done include serologic testing for systemic autoimmune diseases like ANA, anti-cyclic citrullinated peptide [anti-CCP], and rheumatoid factor. As mentioned above, flow cytometry and bone marrow aspiration or cytology remain a gold standard for evaluating immune neutropenia.
It is important to understand that imaging studies do not constitute the evaluation process for autoimmune neutropenia. Hence, unnecessary exposure to radiation should be avoided. However, in case, a lymphoma is suspected in a patient, imaging studies with the help of computed tomography (CT) scan and/or magnetic resonance imaging (MRI) scan can be done. This will help in confirming, locating, and assessing the size of the lymphoma and thus, will aid in early diagnosis and treatment planning.
Splenomegaly can also be evaluated with the help of imaging. Although, it is necessary to understand that presence of splenomegaly alone can not be utilized to confirm the diagnosis of autoimmune neutropenia.
How Can It Be Treated?
The treatment lies upon the diagnosis of the underlying condition or causative factors. In case of infection, antibiotics can be prescribed. The signs and symptoms can be managed with medication. However, autoimmune neutropenia does not require any strong medical or surgical intervention commonly but requires regular monitoring and follow-ups.
Conclusion
Autoimmune neutropenia leads to a decrease in the neutrophil count which can lead to infection, more commonly in children. You can consult a specialist to know more about this condition using online medical platforms.
