Pediatric Autoimmune Neutropenia

Immune neutropenia in children may be classified into autoimmune neutropenia and alloimmune neutropenia. The former then can be divided into primary autoimmune neutropenia (PAIN) and secondary autoimmune neutropenia (SAIN). PAIN is most common during infancy and early childhood (median age of onset 0.77 years),[3] whereas SAIN is more common in older children (median age of onset 10.07 years). SAIN occurs in a setting of systemic autoimmune disease, infection, neoplasia, bone marrow or organ transplantation, drug administration, or immunodeficiency and develops more frequently in girls. Virtually all PAIN resolves before age 5 years, while it is a rare occurrence for SAIN to resolve on its own. Serious infections in PAIN are uncommon, although a variety of infections have been reported. Some patients experience frequent oral ulcers, gingivitis, otitis media, upper respiratory infection, or tonsillopharyngitis; for these individuals, a trial of prophylactic antibiotics may be indicated. In rare cases, serious infections, such as perianal abscess with fistula formation,[10] or even multiple brain abscesses,[11] can occur. The uncommon patients who experience severe infections such as abscesses, mastoiditis, pneumonia, or sepsis would benefit from periodic administration of G-CSF.

Serious, life-threatening infections (sepsis, pneumonia, skin/soft tissue abscesses, osteomyelitis, otomastoiditis, meningitis/encephalitis) occur frequently in children with SAIN.[3]  A study by Farruggia et al reported the frequency of severe infection for PAIN to be 12%, with that of SAIN being 40%.[3] Use of prophylactic antibiotics and regular administration of G-CSF (filgrastim) to prevent severe neutropenia is frequently required in SAIN. Cytopenias arising from other cell lineages, such as immune thrombocytopenic purpura (ITP) and/or autoimmune hemolytic anemia (AIHA), quite often accompany the neutropenia in SAIN.[12] A significant number of patients with SAIN may have an enlarged liver and/or spleen, while in PAIN, these organs are not enlarged. Some patients whose presentation initially indicates PAIN may have a RAG (recombination-activating gene) mutation that is associated with systemic autoimmune disease. These patients may develop autoimmune hemolytic anemia and/or autoimmune thrombocytopenia, in addition to neutropenia.[13]

Some authors divide PAIN into autoimmune neutropenia, in which patients are demonstrated to have auto-antibodies, and chronic idiopathic neutropenia (CIN), in which no such antibodies can be found.[1, 14, 8]  In children, however, presentations, demographics, signs, symptoms, and prognosis are the same;[14] thus, from the point of patient management, demonstration of antibodies is not required. Antibodies found in patients with PAIN have overwhelmingly been those that act against neutrophil-specific antigens, ie, anti–human neutrophil antigen (HNA)-1 antibodies (most common), anti–HNA-3 antibodies, and anti–HNAB antibodies. Of 38 patients with persistent neutropenia who were assayed in a study, only three exhibited antibodies against major histocompatibility complex (MHC) class1 and/or MHC class 2 antigens alone, without antibodies against HNA.[15]  On the other hand, in a rare instance, antibodies were demonstrated in patients who were proven to have severe congenital neutropenia due to a mutation of the ELANE gene.[7]  Therefore, demonstration of anti-neutrophil antibodies does not directly indicate the etiologic role of antibodies in neutropenia.

Alloimmune neutropenia in children are almost exclusively seen in neonates secondary to a mismatch in HNA between the mother and her offspring. The neutropenia can be very severe, but spontaneous recovery is the rule.

A case of secondary autoimmune neutropenia. This patient presented with recurrent otitis and areas of cellulitis in the diaper area. Pseudomonas aeruginosa and Staphylococcus aureus were isolated from the skin lesions. Autoimmune hemolytic anemia and autoimmune neutropenia were confirmed based on the presence of autoantibodies. The patient has a mutation on exon 15, A504T, which changed an asparagine residue to a valine residue.

Lalezari and colleagues demonstrated neutrophil antibodies in 119 of 121 infants and children with chronic neutropenia, thereby establishing the autoimmune nature of the disease.[16] In the study, all patients had at one time an ANC of less than 500/µL (see the Absolute Neutrophil Count calculator).

AIN is similar to immune thrombocytopenic purpura (ITP) of young children, a more common cytopenia in pediatric patients. ITP is believed to be triggered by a viral infection and, in some individuals, by immunization. Whether AIN is commonly triggered by similar etiologies is unknown. A similar age group is affected, and recovery is expected in both disorders. Nakamura et al showed deficiencies in regulatory T cells (CD4+, CD25+) in children with AIN;[17] thus, the disease may be a phenomenon of physiologically delayed maturation of immune regulation.

Some studies, moreover, have shown an association between AIN and parvovirus B19 infection.

A literature review by Farmer et al determined that autoimmune cytopenias, including AIN, were associated with up to 84.1% of RAG protein deficiencies.[13] The median age of onset found for AIN in RAG-deficient patients, 2.6 years, was significantly older than that for other children with AIN. In the cohort with RAG protein deficiency, no patients had neutropenia alone. Instead, all of them had other cytopenias, such as autoimmune hemolytic anemia (AIHA) or ITP; granulomas; or evidence of immune deficiency or immune dysregulation (autoimmune lymphoproliferative syndrome [ALPS]–like disorder, severe combined immunodeficiency [SCID], or atypical SCID). The investigators also found that in 71.4% of cases, RAG deficiency–associated AIN was refractory to intravenous immunoglobulin, steroids, and rituximab.[13]

In AIN, antibodies most commonly include immunoglobulin G (IgG) against neutrophil glycosylated isoforms of Fc gamma RIIIb (or CD 16b) and HNA-1 and, less commonly, against HNA-4..

Although anti-HLA antibodies may be present in AIN, they are very rarely the cause of the disorder.

In PAIN, antibodies, if detected, are almost exclusively against the NA alloantigens, although at the onset of neutropenia, in rare instances, antibodies against Fc gamma RIIIb may be present (see below). On the other hand, children with SAIN usually show antibodies with pan–Fc gamma RIIIb specificity, not anti NA-alloantigens.[18]

Bone marrow examination findings in AIN are variable and not diagnostic. Bone marrow may be normal, show late-stage maturation arrest, or be hyperplastic or hypoplastic. In rare cases, granulocyte phagocytosis has been reported.[19]

In a study by Perdikogianni et al, circulating G-CSF levels (serum or plasma) were found to be normal in AIN, even during the neutropenic period, except when patients had infections.[20] On the other hand, Kobayashi et al found that the patient’s sera contained a mildly but significantly elevated concentration of G-CSF compared with the control sera.[21]

A Danish study, by Kløve-Mogensen et al, indicated that blood type O and secretion of H Leb antigens are protective against AIN. The investigators found that 36.4% of study patients with AIN were type O, compared with 46.8% of controls, while 25.2% of individuals with AIN demonstrated H Leb antigen secretion, versus 35.0% of controls.[22]

The incidence of autoimmune neutropenia does not vary among different ethnic populations.

A Scottish study estimated that in the Scottish population, the incidence of autoimmune neutropenia is 1 in 100,000 children per year.[23] This may have been an underestimate, however, because laboratory tests are not usually performed in most cases of autoimmune neutropenia.

Autoimmune neutropenia has a slight preponderance in girls in one study,[16] but not in others.[24] The mean age at diagnosis of autoimmune neutropenia is 6-12 months, with a range of 3-30 months.

A high frequency of benign (ethnic) neutropenia is widely recognized in African Americans, Yemenite and Falasha Jews, Black Beduin, blacks of South African extraction, Ethiopians, West Indians, Arab Jordanians, and various tribal groups inhabiting the United Arab Emirates.[25]   A study showed the median ANC of children with benign ethnic neutropenia to be 893 x 106/L.[26] The gene responsible for this form of neutropenia is identified as the DARC (Duffy antigen/receptor chemokine) gene, although the exact mechanism that causes neutropenia is still to be elucidated.[27, 28] In the age group (6 months to 3 years) when AIN is common, it may be impossible to distinguish these two entities in a given child.

Morbidity

Infections associated with primary AIN, which are usually limited and mild, include just fever, otitis media, upper respiratory tract infection, common colds, viral gastroenteritis, skin infection, stomatitis, and gingivitis. Sepsis and pneumonia are rare. Hajishengallis et al reported on the development of AIN-related periodontal disease in a child aged 2 years.[29] In a study done at St Jude Children’s Research Hospital on children with all types of chronic neutropenia, otolaryngological infections predominated, consisting of recurrent otitis media (81%), viral upper respiratory tract infection (67%), oral ulcers or gingivitis (53%), tonsillitis (39%), and sinusitis (37%).[30]

A case of secondary autoimmune neutropenia. This patient presented with recurrent otitis and areas of cellulitis in the diaper area. Pseudomonas aeruginosa and Staphylococcus aureus were isolated from the skin lesions. Autoimmune hemolytic anemia and autoimmune neutropenia were confirmed based on the presence of autoantibodies. The patient has a mutation on exon 15, A504T, which changed an asparagine residue to a valine residue.

This is in contrast to the severe, life-threatening infections (quite often systemic) experienced by infants with severe congenital neutropenia (Kostmann disease and other types), children with aplastic anemia, older children with secondary AIN, and children with neutropenia who are receiving chemotherapy. An Italian study showed that 40% of children with secondary AIN had severe infections, as compared with 12% of children with primary AIN.[3]

In another study, of 73 children with neutropenia, Fioredda et al reported a rate of 0.66 infections per patient with AIN, compared with 5.75 infections per patient with severe congenital neutropenia.[31]  (The AIN figure may be an overestimate, however, since there may have been a selection bias; the neutropenia registry used in the study contained more severely affected AIN patients.) The reasons for this difference between primary autoimmune and severe congenital neutropenia may be related to the fact that individuals with AIN have an adequate bone marrow neutrophil reserve and can therefore mount some level of neutrophil response to an infection, even though these neutrophils are rapidly destroyed; this is in contrast to patients with poor or no bone marrow reserve.

Although febrile illnesses appear to be more common in children with AIN than in healthy children, AIN usually does not affect the child's growth and development, although some exceptions occur. (See History.)

The prognosis in primary chronic neutropenia is excellent. The condition usually lasts only 2-3 years before spontaneous resolution, and virtually all patients recover by age 5 years.

Spontaneous recovery after 6-24 months is typical. If it persists beyond age 4-5 years, consider other diagnoses (secondary neutropenia). It is important to follow these patients into recovery for this reason.

Thoroughly discussing the natural history with the patient’s parents and/or caregivers is important, since this can prevent undue anxiety created by low neutrophil counts.

In addition, because medical advice is usually sought after infections have occurred in a child with autoimmune neutropenia, discussing the condition’s natural history validates the experience of the parents and/or caregivers and, in turn, increases their confidence in the physician's diagnosis and treatment.

It is important for patients to maintain good dental hygiene in order to prevent gingivitis, stomatitis, and other mucous membrane infections of the mouth.

Most children with autoimmune neutropenia receive initial medical attention because of the occurrence of a febrile illness during the last 6 months of infancy. Such illnesses include the following:

• A simple febrile illness

• Acute otitis media

• Upper respiratory tract infection

• Pneumonia

• Gastroenteritis

• Tonsillitis/pharyngitis

• Skin infection

For primary AIN, a family history of neutropenia, leukopenia, and consanguinity is absent. This is in contrast to congenital neutropenia or ethnic (or familial) neutropenia. If a complete blood count (CBC) is performed earlier in the child's life, it is usually within the reference range.

Children with autoimmune neutropenia may have a history of frequent upper respiratory infections or of other infections listed above. However, serious, life-threatening infections, such as sepsis, osteomyelitis, deep tissue cellulitis/abscess, or bacterial meningitis, are very rare. Some patients are asymptomatic. A CBC performed for an unrelated reason, such as a routine CBC, may reveal neutropenia.

A family history of neutropenia or consanguinity, a history of serious past infections, or documentation of past neutropenia in the child significantly favors the diagnosis of congenital neutropenia or a secondary neutropenia including immunodeficiency, rather than acquired AIN, and indicates a worse prognosis.[32]

Physical examination may reveal signs of a local infection, including mouth ulcer, gingivitis, upper respiratory tract infections, impetigo, otitis media, pneumonia, and, very rarely, cellulitis, abscesses, or sepsis.

Many children may simply present with fever without any focal infection or they may physically be entirely normal. Patients generally do not exhibit growth failure or chronic illness.

Neutropenia is usually discovered during the workup of a febrile illness. Leukopenia and neutropenia are also often discovered incidentally, as a result of a routine CBC or a CBC performed for an unrelated reason.

The clinical severity and frequency of infections, rather than the severity of neutropenia, should dictate the extent of laboratory workup, since finding a periodic drop in the neutrophil count to zero is not uncommon in AIN.[38]  Lindqvist et al published an algorithm for the workup of children with neutropenia that may be practical and helpful.[14]

Go to Neutropenia for complete information on this topic.

A CBC demonstrates a white blood cell (WBC) count that is either decreased or within the reference range and a neutrophil count of less than 1000/µL in infants and < 1500/μL in older children.

Performing sequential CBCs with differential to document chronicity is important, because most neutropenia in infants resolves with recovery from an acute infection. In individuals with autoimmune neutropenia, the absolute neutrophil count often remains less than 500 (see the Absolute Neutrophil Count calculator).

Monocytosis and eosinophilia may occur, although significant eosinophilia or monocytosis is rare, unlike in severe congenital neutropenia. In individuals with primary autoimmune neutropenia, hemoglobin and platelet counts are normal. In patients with secondary autoimmune neutropenia, associated anemia, an increased reticulocyte count due to hemolysis, and thrombocytopenia may be present. Presence of immature white blood cells, including blasts, suggests leukemia.

Antinuclear antibodies may be positive in patients with secondary autoimmune neutropenia, although only rarely in infants. Direct antiglobulin test (DAT) or direct Coombs test results may be positive in individuals with secondary autoimmune neutropenia; perform this study when evidence of hemolysis or thrombocytopenia (Evan syndrome) is present.

Multi-lineage cytopenias virtually exclude AIN, and other etiologies should be promptly considered.

Documentation of neutrophil antibodies is not always necessary for patients with a benign course of AIN. In addition, an absence of demonstrable antineutrophil antibodies does not exclude the diagnosis. The age of onset, a benign clinical course, and normal bone marrow findings are sufficient to make a diagnosis of PAIN. In addition, research has indicated that, in some patients, antibodies detected at the onset are not detectable on retesting before the patient has recovered.[37] Thus, antibody test findings may not always be positive, depending on the timing. Also, sensitivity for antibody detection varies depending on the test. The indirect granulocyte immunofluorescence test (GIFT) is more sensitive than monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA). It appears that panantibodies to Fc gamma RIIIb are positive during the early period of neutropenia, but they disappear earlier than HNA-1 antibodies.[9]  (Patients with detectable antineutrophil antibodies may have congenital neutropenia due to ELANE mutation. In these instances, early initiation of G-CSF may be lifesaving.[7] ) Boxer et al found no difference in the rate of spontaneous recovery between antibody-positive and antibody-negative patients with chronic autoimmune (or idiopathic) neutropenia, casting significant doubt on the usefulness of antibody testing.[7]

Bone marrow examination is often necessary to exclude other diagnoses, in particular leukemia, although bone marrow findings are not diagnostic of this disorder.

The bone marrow may be hypercellular or normocellular with myeloid hyperplasia. However, it can be completely normal, including physiologic lymphoid hyperplasia.

In clinically severe instances of AIN, "maturation arrest" may be observed, in that there is a paucity or absence of mature neutrophils. However, a preponderance of myelocytes, metamyelocytes, and bands may be present. In rare instances, intramedullary phagocytosis of granulocytes may be observed.[19]

Serum immunoglobulin quantitation helps to exclude neutropenia associated with hypogammaglobulinemia or hyper-IgM syndrome.

In most instances, bone marrow findings are normal. Maturation arrest at promyelocyte or myelocyte stage typically seen in severe congenital neutropenia is absent. Absence of leukemic blasts excludes a diagnosis of leukemia.

Often, an increased number of mature lymphocytes consistent with the patient's age are present.

Although, as previously indicated, demonstration of anti-neutrophil antibodies is not necessary to establish the diagnosis of PAIN, there are several tests available to reveal such antibodies. The most commonly used one is the indirect granulocyte immunofluorescence test (I-GIFT), which detects circulating antibodies in the patient's serum. The direct GIFT (D-GIFT) detects neutrophil-bound antibodies on the patient's cells. D-GIFT currently is available only in research laboratories; it is difficult to perform due to the reduced number of neutrophils in patient samples. Porretti et al reported higher sensitivity for D-GIFT compared with I-GIFT, but there were many false-positive results with this test, showing lower specificity.[4]

In addition to the GIFTS, other tests used to detect anti‐HNA antibodies are the granulocyte agglutination test (GAT) and monoclonal antibody–specific immobilization of granulocyte antigens (MAIGA).[6] These tests require fresh control granulocytes from volunteers, and thus are difficult to perform in routine clinical laboratories. Because of this limitation, Onodera et al developed the extracted granulocyte antigen immunofluorescence assay (EGIFA).[6] By using prepared extracted human HNAs (HNA-1a, -1b , and -2) bound to microspheres, the investigators were able to determine the intensity of immunofluorescence associated with the patient's serum through antibodies reacting with respective antigens. The procedure, however, is extremely cumbersome and not reproduced by other laboratories. Some investigators have used fresh-frozen bone marrow slides to detect anti-HNA instead of blood slides; a 53% sensitivity and 100% specificity were reported using the bone marrow slides.[39]

Focus the treatment of autoimmune neutropenia on intercurrent infections. In patients with frequent infections, prophylactic antibiotics with trimethoprim and sulfamethoxazole may help, although the benefits are anecdotal,[9] and no randomized, controlled trials have been done. In children with recurrent infections, treatment with G-CSF (Neupogen) greatly decreases frequency of infections.

If the patient is free from significant infection, treatment is unnecessary.

An invasive procedure, such as a splenectomy, is not warranted, because virtually all patients spontaneously recover from chronic neutropenia.

Spontaneous recovery after 6-24 months is typical. If it persists beyond age 4-5 years, consider other diagnoses. It is important to follow these patients into recovery for this reason.

Go to Neutropenia for complete information on this topic.

Hematologic consultation is recommended to exclude other causes of neutropenia, in particular severe congenital neutropenia and acute lymphoblastic leukemia, and to obtain assistance in the interpretation of neutrophil antibody studies.

Once the diagnosis of autoimmune neutropenia is firmly established, primary care physicians can monitor patients.

Patients with frequent infections may benefit from prophylactic antibiotics with trimethoprim and sulfamethoxazole.

G-CSF (Filgrastim, Neupogen) has been demonstrated to raise neutrophil counts and may be useful for the treatment of persistent or recurrent infections. Intravenous gamma globulin may be used for the same purpose. Reserve these medications for infections that do not respond to conventional antibiotics.

Class Summary

Colony-stimulating factors (CSFs) are used for recurrent or refractory infections that are unresponsive to conventional therapy. They act as a hematopoietic growth factor that stimulates the development of granulocytes. CSFs are used to treat or prevent neutropenia in patients who are receiving myelosuppressive cancer chemotherapy and to reduce the period of neutropenia associated with bone marrow transplantation. These agents are also used to mobilize autologous peripheral blood progenitor cells for bone marrow transplantation and in the management of chronic neutropenia.

Filgrastim (G-CSF, Neupogen)

This is a G-CSF that activates and stimulates production, maturation, migration, and cytotoxicity of neutrophils. It is recommended only for patients with a clinically significant history of frequent infections.

Class Summary

Immunoglobulins are used for infections that are unresponsive to conventional measures. Immunoglobulins are used for passive immunization, thus conferring immediate protection against some infectious diseases.

Immune Globulin, Intravenous (Carimune NF, Gammagard S/D)

This agent consists of purified IgG from human plasma; all commercially available products are viral inactivated.

Class Summary

These agents are used for the prevention of frequent infections.

Trimethoprim and sulfamethoxazole (Bactrim, Septra)

This drug combination inhibits bacterial growth by inhibiting the synthesis of dihydrofolic acid. It may help frequent infections (eg, otitis media); however, the dose for this indication has not been established (no clinical studies have demonstrated the efficacy of this drug).

Class Summary

Various therapies are available that may increase the neutrophil count to normal levels temporarily in children with chronic benign neutropenia, which include corticosteroids. Corticosteroids may be useful in patients not responding to other therapies. Routine use of steroids in children with neutropenia is strongly discouraged. Do not use steroids just to increase the counts.

Prednisone

Corticosteroids such as prednisone can be used to suppress the antibody formation and increase the neutrophil count. Use of steroids in this disorder is only anecdotal Routine use of steroids in uncomplicated neutropenia is strongly discouraged. Large doses may be required, potentially leading to adverse effects such as increased risk of infection.