Several autoimmune diseases can cause low neutrophils, a condition called autoimmune neutropenia. The most direct form is primary autoimmune neutropenia, where the immune system produces antibodies that target and destroy neutrophils specifically. But neutropenia also shows up as a complication of broader autoimmune conditions, with lupus, Felty syndrome, and Sjögren’s syndrome among the most recognized culprits. The mechanisms differ depending on the disease, and so do the risks.
Primary Autoimmune Neutropenia
Primary autoimmune neutropenia is the condition where the immune system attacks neutrophils directly, without another autoimmune disease driving the process. It is overwhelmingly a disease of infancy and early childhood. Antibodies, usually targeting a receptor on the neutrophil surface called FcγRIIIb, bind to neutrophils and mark them for destruction. It is the most common cause of neutropenia in children under about three to four years old.1PubMed Central. Diagnosis and management of primary autoimmune neutropenia in children: insights for clinicians In one cohort from Romania, the median age at onset was about seven and a half months, and roughly three-quarters of affected children had severe neutropenia at some point during the disease.2PubMed Central. Primary autoimmune neutropenia of infancy and childhood in a cohort of patients from western Romania
The good news for parents is that the childhood form almost always resolves on its own. In a small but well-followed group of children, the neutropenia cleared up within about six months to just over three years, with a median of around thirteen months. None required immunosuppressive therapy, and routine antibiotics were enough to manage the infections that came up, which were mostly ear infections and upper respiratory illnesses.3PubMed. Natural history of primary autoimmune neutropenia in infancy That self-limited course is a critical distinction, because the same condition in adults behaves quite differently.
When primary autoimmune neutropenia appears in adults, it tends to be chronic and far less likely to resolve spontaneously. Women are affected more often than men, and the condition may persist indefinitely. The antibodies target the same neutrophil surface proteins, but the immune system’s tendency to self-correct that children benefit from does not seem to operate as reliably in adults.4PubMed Central. Primary and secondary autoimmune neutropenia
Lupus
Systemic lupus erythematosus is one of the most common autoimmune diseases to cause low neutrophils as part of a broader pattern of blood cell problems. In a large study comparing lupus patients with and without neutropenia, about one in five lupus patients had neutropenia. Those who did were also far more likely to have low platelet counts and low lymphocyte counts at the same time, suggesting that lupus tends to attack multiple blood cell lines rather than singling out neutrophils alone.5RMD Open. Systemic lupus erythematosus and neutropaenia: a hallmark of haematological manifestations
One specific antibody connection stands out. Patients with lupus who carry anti-Ro/SSA antibodies are significantly more likely to develop neutropenia. In one study, lupus patients positive for anti-Ro antibodies were roughly seven and a half times more likely to have low neutrophil counts compared to lupus patients without those antibodies. The researchers found evidence that anti-Ro antibodies can cross-react with a protein on the neutrophil surface, meaning the immune system mistakes neutrophils for a target because of a molecular resemblance.6PubMed Central. Association of neutropenia in systemic lupus erythematosus (SLE) with anti-Ro and binding of an immunologically cross-reactive neutrophil membrane antigen This cross-reactivity is a recurring theme across autoimmune neutropenias: the antibody was made against something else, but it happens to bind neutrophils too.
Felty Syndrome and Rheumatoid Arthritis
Felty syndrome is the classic intersection of rheumatoid arthritis and neutropenia. It is defined by a triad: long-standing, seropositive rheumatoid arthritis with destructive joint disease, an enlarged spleen, and low neutrophil counts.7The Open Rheumatology Journal. Felty’s Syndrome, Insights and Updates The neutropenia in Felty syndrome does not come from a single mechanism. Instead, it is driven by at least three forces working together: the enlarged spleen traps and destroys neutrophils, antibodies coat neutrophils and accelerate their removal from the bloodstream, and the bone marrow’s ability to produce enough replacement neutrophils may be impaired.
A granulocyte-specific anti-nuclear factor is found in a very high proportion of Felty syndrome patients. Reports put the rate at around 75 to 100 percent, compared with only 25 to 30 percent in rheumatoid arthritis patients without Felty syndrome. On top of that, IgG-type antibodies against granulocytes circulate in the blood and further contribute to neutrophil destruction. T-cell activation may also suppress neutrophil production in the bone marrow.8PubMed Central. Rheumatoid arthritis patients with peripheral blood cell reduction should be evaluated for latent Felty syndrome: A case report
There is an important practical wrinkle for anyone with rheumatoid arthritis who learns their neutrophil count is low. Medications are actually the most common cause of neutropenia in RA patients, not the disease itself. Many drugs used to treat RA can suppress neutrophil production as a side effect. A detailed medication review is the first diagnostic step before autoimmune mechanisms are blamed. If neutropenia persists after medication causes are ruled out and the spleen is enlarged, Felty syndrome enters the picture. Felty syndrome is also associated with large granular lymphocytic leukemia in a substantial fraction of cases, estimated at around 40 percent, so the workup can become involved.9PubMed. Management of neutropenia in patients with rheumatoid arthritis
Sjögren’s Syndrome
Sjögren’s syndrome, best known for dry eyes and dry mouth, also causes blood cell abnormalities more often than people expect. Neutropenia is one of the hematologic complications that can appear as part of the systemic autoimmune process.10PubMed Central. Clinical Phenotype and Mechanisms of Leukopenia/Neutropenia in Patients with Primary Sjögren’s Syndrome In a study of about 300 patients with primary Sjögren’s syndrome, roughly a third developed neutropenia during follow-up. When drug-related and cancer-related causes were excluded, about 30 percent still had neutropenia that appeared to be driven by the autoimmune disease itself.11PubMed. Prevalence and clinical relevance of autoimmune neutropenia in patients with primary Sjögren’s syndrome
That study also found that neutropenia in Sjögren’s correlated with anti-Ro/La antibodies, the same family of autoantibodies linked to neutropenia in lupus. The connection hints at shared immune mechanisms between these diseases. Neutropenia in Sjögren’s patients also tended to occur alongside other low blood counts and was associated with a higher rate of serious infections, making it a clinically relevant finding rather than a harmless lab curiosity.11PubMed. Prevalence and clinical relevance of autoimmune neutropenia in patients with primary Sjögren’s syndrome
Other Autoimmune Conditions Linked to Low Neutrophils
ANCA-associated vasculitis involves a different relationship with neutrophils. In this group of diseases, which cause inflammatory damage to small blood vessels, the immune system produces antibodies against proteins inside neutrophils themselves, specifically myeloperoxidase and proteinase 3. These antibodies activate neutrophils rather than simply marking them for destruction, causing them to damage blood vessel walls. The neutropenia that sometimes occurs in vasculitis can result both from the immune attack on neutrophils and from the immunosuppressive drugs used to treat the condition.12PubMed Central. Neutrophils in ANCA-associated vasculitis: Mechanisms and implications for management
Autoimmune thyroid disease, particularly Hashimoto’s thyroiditis, has also been associated with neutropenia. This is an area where the evidence is thinner, but abnormalities in white blood cell counts have been described as an early sign of autoimmunity in patients with Hashimoto’s.13Endocrine Abstracts. Leukopenia A Benign Comorbitidy and Early Sign of Autoimmunity in Hashimoto’s Thyroiditis The broader pattern is that many autoimmune conditions can produce neutropenia as a secondary feature. The conditions mentioned above are the most frequently implicated, but secondary autoimmune neutropenia has also been reported alongside lymphoproliferative disorders and certain viral infections.14Autoimmunity Reviews. Autoimmune neutropenia in adults
How Autoimmune Neutropenia Happens at the Cellular Level
Whatever the underlying autoimmune disease, the core problem is the same: antibodies bind to proteins on the neutrophil surface and trigger their removal. The most common target is a receptor called HNA-1 (human neutrophil antigen 1), located on the FcγRIIIb protein. Five distinct neutrophil antigen systems have been identified, and antibodies against any of them can potentially cause neutropenia.15PubMed Central. Molecular Genetics of the Human Neutrophil Antigens In some patients, the antibodies target adhesion proteins called CD11b/CD18, which neutrophils use to stick to blood vessel walls and migrate to infection sites. Antibodies against these proteins may not only lower neutrophil numbers but also impair the function of the neutrophils that remain, compounding infection risk.16Blood. Identification of autoantibodies specific for the neutrophil adhesion glycoproteins CD11b/CD18 in patients with autoimmune neutropenia
Once antibodies coat a neutrophil, the cell is cleared from circulation primarily in the liver and spleen. The spleen’s role is thought to mirror what happens in autoimmune hemolytic anemia, where antibody-coated red blood cells are trapped and destroyed in splenic tissue.17PubMed Central. Autoimmune Neutropenias: Update on Clinical and Biological Features in Children and Adults In Felty syndrome, where the spleen is already enlarged, this splenic sequestration is especially pronounced.
Diagnosing Autoimmune Neutropenia
Proving that neutropenia is autoimmune in origin requires detecting the offending antibodies, which is not straightforward. The International Granulocyte Immunobiology Workshop recommends using two tests together: the granulocyte immunofluorescence test and the granulocyte agglutination test, supplemented by a confirmatory assay called MAIGA. The immunofluorescence test uses fixed neutrophils to detect antibody binding, while the agglutination test uses live neutrophils and looks for antibody-triggered clumping. The MAIGA assay helps pin down which specific neutrophil antigen the antibody targets.18ISBT Science Series. The fundamentals of neutrophil antigen and antibody investigations
In practice, these tests have limited sensitivity. Antineutrophil antibodies can be intermittently detectable, and false negatives are common. A single negative antibody test does not rule out autoimmune neutropenia, and clinicians often need to repeat testing or rely on the clinical picture — a patient with an autoimmune disease whose neutropenia has no other obvious cause may be treated as having autoimmune neutropenia even without a definitive antibody result.
There is also a diagnostic pitfall worth knowing about. A phenomenon called EDTA-dependent pseudoneutropenia can make neutrophil counts look artificially low. The anticoagulant used in standard blood collection tubes (EDTA) can occasionally cause neutrophils to clump together, and the machine that counts cells reads the clumps as fewer individual cells. In a series of patients where this was investigated, the clumping involved only neutrophils and appeared to be driven by IgM antibodies reacting with EDTA-modified cell surfaces.19PubMed. Studies on EDTA-dependent pseudoneutropenia If a low neutrophil count does not match the clinical picture, collecting blood in a different anticoagulant and rechecking is a simple way to catch this artifact.
Drug-Induced Neutropenia Versus Autoimmune Causes
One of the most important distinctions for anyone with an autoimmune disease and a low neutrophil count is whether the disease or the medication is responsible. Many drugs used to manage autoimmune conditions can suppress neutrophil production. Biologic therapies deserve special attention here: an estimated 10 percent incidence of neutropenia has been reported with several classes of biologics, including TNF-alpha inhibitors, IL-6 inhibitors, and anti-CD52 agents. Severe neutropenia and sepsis from these drugs are less common but have been documented.20PubMed Central. State of Art of Idiosyncratic Drug-Induced Neutropenia or Agranulocytosis, with a Focus on Biotherapies
The clinical approach is usually sequential: review medications first, consider dose adjustments or drug switches, and only investigate autoimmune mechanisms if neutropenia persists after drug-related causes are excluded. This ordering matters because drug-induced neutropenia is both more common and more straightforwardly fixable.
Treatment When Neutrophils Stay Low
For primary autoimmune neutropenia in children, treatment is often unnecessary beyond watchful waiting and antibiotics for infections as they arise. The condition resolves on its own in the vast majority of cases. For adults with chronic autoimmune neutropenia, or for secondary autoimmune neutropenia complicating diseases like lupus or Felty syndrome, the approach depends on how severe the neutropenia is and how frequently infections occur.
Granulocyte colony-stimulating factor (G-CSF) is the most established treatment for boosting neutrophil production. It stimulates the bone marrow to produce more neutrophils, and in autoimmune neutropenia specifically, it has not been observed to worsen the neutropenia over time.21PubMed Central. Outcomes for patients with severe chronic neutropenia treated with granulocyte colony-stimulating factor One case report found something unexpected: when G-CSF was started, not only did the neutrophil count rise, but the antineutrophil antibodies themselves disappeared. When the drug was tapered, the antibodies came back and neutropenia returned. The researchers proposed that G-CSF floods the bloodstream with so many neutrophils and soluble receptor fragments that the circulating antibodies get absorbed, effectively mopping them up.22British Journal of Haematology. The use of rhG-CSF in chronic autoimmune neutropenia: reversal of autoimmune phenomena, a case history
Rituximab, an antibody therapy that depletes B cells (the cells that make antibodies), is sometimes tried for autoimmune cytopenias. It works well for some autoimmune blood conditions, but its track record for autoimmune neutropenia specifically is less impressive. In one study of low-dose rituximab for various autoimmune cytopenias, the drug had no effect on the patient with autoimmune neutropenia, even while other patients with different types of cytopenias responded.23Haematologica. Activity and safety profile of low-dose rituximab for the treatment of autoimmune cytopenias in adults This does not mean rituximab never works for neutropenia, but it highlights that autoimmune neutropenia can be stubbornly resistant to therapies that succeed in related conditions.
How Childhood and Adult Forms Differ
The gap between pediatric and adult autoimmune neutropenia goes beyond just whether the condition resolves on its own. Data from an Italian registry compared children with typical primary autoimmune neutropenia to patients with late-onset forms and those whose neutropenia lasted longer than expected. The late-onset and long-lasting groups had strikingly higher rates of additional autoimmune markers and autoimmune diseases compared with children whose neutropenia followed the standard childhood pattern. They also had lower B-cell and natural killer cell counts, were more likely to need G-CSF treatment, and were less likely to achieve resolution.24Blood Advances. Late-onset and long-lasting autoimmune neutropenia: an analysis from the Italian Neutropenia Registry
This finding suggests that what looks like “the same disease” in a toddler and in an adult may actually represent different immunological problems. The childhood version appears to be a limited, self-correcting immune mistake. The adult version, or the childhood version that refuses to go away, is more likely to be a window into broader immune dysregulation. For clinicians, a neutropenia that starts after early childhood or persists beyond the expected timeline should prompt a wider autoimmune workup, not just antibody testing against neutrophils.
When Neutrophil Function Matters More Than Count
Neutrophil numbers get most of the attention, but some autoimmune conditions also impair how well the remaining neutrophils work. In inflammatory bowel disease, for example, neutrophils from patients with Crohn’s disease and ulcerative colitis produce less superoxide, one of the key chemicals neutrophils use to kill bacteria. At the same time, levels of a protective enzyme called superoxide dismutase were reduced in these cells.25Gut / BMJ Publishing Group. Diminished neutrophil function in Crohn’s disease and ulcerative colitis identified by decreased oxidative metabolism and low superoxide dismutase content In autoimmune neutropenia where antibodies target the adhesion protein CD11b/CD18, the antibodies may directly interfere with neutrophils’ ability to reach infection sites, even if the absolute count is not dramatically low.16Blood. Identification of autoantibodies specific for the neutrophil adhesion glycoproteins CD11b/CD18 in patients with autoimmune neutropenia A patient whose neutrophil count is only mildly reduced but whose neutrophils are also functionally impaired can face infection risks out of proportion to what the number alone would suggest. This is an underappreciated dimension of the problem that standard blood counts do not capture.