Old and new faces of neutropenia in children

Clinical significance of human neutrophil antigen-1 antibodies in children with neutropenia

Primary autoimmune neutropenia in young children is characterized by chronic neutropenia and positivity for antibodies against human neutrophil antigens (HNAs). This study analyzed the clinical characteristics of 402 children with neutropenia to identify differences between those with and without HNA-1 antibodies (HNA1abs). HNAabs in sera were detected by granulocyte immunofluorescence testing using flow cytometry. Relative fluorescence intensity (RFI) values were used to divide patients into positive (PG, n = 302), borderline (BG, n = 34), and negative (NG, n = 66) groups. The antibodies reacted to HNA-1a alone (59%), HNA-1b alone (1%), and HNA-1a/1b (40%). The PG had a significantly lower absolute neutrophil count before definitive diagnosis and a 1.6- to 2-times greater risk of hospitalization during neutropenia than the other groups. The median duration of neutropenia was longest in the PG at 25 months, followed by 20 months in the BG and 14 months in the NG. This large-scale cohort characterizes clinically distinct groups using the RFI value for HNA1abs in young children with neutropenia. Detection of HNA1abs may aid in understanding the clinical characteristics of children with neutropenia.

Autoimmune Neutropenia and Immune-Dysregulation in a Patient Carrying a TINF2 Variant

In recent years, the knowledge about the immune-mediated impairment of bone marrow precursors in immune-dysregulation and autoimmune disorders has increased. In addition, immune-dysregulation, secondary to marrow failure, has been reported as being, in some cases, the most evident and early sign of the disease and making the diagnosis of both groups of disorders challenging. Dyskeratosis congenita is a disorder characterized by premature telomere erosion, typically showing marrow failure, nail dystrophy and leukoplakia, although incomplete genetic penetrance and phenotypes with immune-dysregulation features have been described. We report on a previously healthy 17-year-old girl, with a cousin successfully treated for acute lymphoblastic leukemia, who presented with leukopenia and neutropenia. The diagnostic work-up showed positive anti-neutrophil antibodies, leading to the diagnosis of autoimmune neutropenia, a slightly low NK count and high TCR-αβ+-double-negative T-cells. A next-generation sequencing (NGS) analysis showed the 734C>A variant on exon 6 of the TINF2 gene, leading to the p.Ser245Tyr. The telomere length was short on the lymphocytes and granulocytes, suggesting the diagnosis of an atypical telomeropathy showing with immune-dysregulation. This case underlines the importance of an accurate diagnostic work-up of patients with immune-dysregulation, who should undergo NGS or whole exome sequencing to identify specific disorders that deserve targeted follow-up and treatment.

Inherited Bone Marrow Failure Syndromes: Biology and Diagnostic Clues

Inherited bone marrow failure syndromes are a group of genetic disorders associated with bone marrow production defects resulting in single or multiple cytopenias. Many of these disorders predispose the patient to hematologic and nonhematologic malignancies, requiring life-long follow-up. A positive family history of hematologic disorders or malignancies is frequent, as these disorders commonly run in families, and selection of family members as potential bone marrow donors should be performed with caution to avoid transplanting potentially defective stem cells. This review highlights the most common genetic disorders associated with bone marrow failure.

Incidence of Severe Chronic Neutropenia in South Korea and Related Clinical Manifestations: A National Health Insurance Database Study

Background and objectives: Severe chronic neutropenia (SCN) is a condition in which absolute neutrophil counts remain at a low level (under 500/µL) over months or years. Because of the rare onset of SCN, its epidemiology, prognosis, and clinical manifestations have not yet been fully understood. In particular, large-cohort studies in Asian countries are still insufficient. Therefore, in this study, national health insurance data was used to investigate the epidemiologic features and prognosis of SCN in South Korea. Materials and Methods: The data from the Health Insurance Review and Assessment database recorded between 1 January 2011 and 31 December 2015 were explored. SCN was defined based on the ICD-10 code, registry of benefit extension policy, and inclusion criteria of the study. After identifying patients with SCN, annual incidence and their co-morbidities were analyzed. Results: Among the initially identified patients with severe neutropenia (N = 2145), a total of 367 patients had SCN and were enrolled. The annual incidence rate of SCN ranged from 0.12 to 0.17 per 100,000 person-year (PY) during the study period. The highest incidence was observed in pediatric patients aged between 0 to 9 years (N = 156), followed by women in their fifties (N = 43). The total incidence rate was 0.17 in females and 0.12 in males (Relative risk (RR): 1.43, 95%, CI: 1.16–1.76). The most common accompanying condition was mild respiratory infection, but about 3.2% of patients progressed to hematologic malignancy after an average of 2.4 years. Conclusions: This nationwide population-based epidemiological study showed that incidence of SCN is higher in pediatrics and middle-aged women. As progression to hematologic malignancy was significantly higher in the age of in 45–49 years old, careful follow-up is necessary in this group. However, since this study lacks the molecular information, these finding need to be interpreted with great caution.

Paediatric autoimmune neutropaenia

Neutropaenia is defined as an absolute neutrophil count (ANC) of less than 1500 cells/µL and is often divided into mild (ANC: 1000 to 1500 cells/µL), moderate (ANC: 500 to 1000 cells/µL) and severe (ANC: >500 cells/µL) neutropaenia. Autoimmune neutropaenia is arguably one of the most clinically relevant forms of neutropaenia and is defined by an ANC of <500 cells/µL alongside the confirmed presence of anti-neutrophil antibodies. It is a rare subset of neutropaenia boasting an incidence of just 1 in 100 000 infants and is thought to be caused as a result of a 'surveillance escape event' of the immune system. This case report identifies key issues in the diagnosis and monitoring of paediatric patients with recurrent neutropaenia and reviews current literature relating to its management in hospital and community settings.

New monogenic disorders identify more pathways to neutropenia: from the clinic to next-generation sequencing

Neutrophils are the most common type of leukocyte in human circulating blood and constitute one of the chief mediators for innate immunity. Defined as a reduction from a normal distribution of values, neutropenia results from a number of congenital and acquired conditions. Neutropenia may be insignificant, temporary, or associated with a chronic condition with or without a vulnerability to life-threatening infections. As an inherited bone marrow failure syndrome, neutropenia may be associated with transformation to myeloid malignancy. Recognition of an inherited bone marrow failure syndrome may be delayed into adulthood. The list of monogenic neutropenia disorders is growing, heterogeneous, and bewildering. Furthermore, greater knowledge of immune-mediated and drug-related causes makes the diagnosis and management of neutropenia challenging. Recognition of syndromic presentations and especially the introduction of next-generation sequencing are improving the accuracy and expediency of diagnosis as well as their clinical management. Furthermore, identification of monogenic neutropenia disorders is shedding light on the molecular mechanisms of granulopoiesis and myeloid malignancies.

Elastase inhibitors as potential therapies for ELANE-associated neutropenia

Mutations in ELANE, the gene for neutrophil elastase (NE), a protease expressed early in neutrophil development, are the most frequent cause of cyclic (CyN) and severe congenital neutropenia (SCN). We hypothesized that inhibitors of NE, acting either by directly inhibiting enzymatic activity or as chaperones for the mutant protein, might be effective as therapy for CyN and SCN. We investigated β-lactam-based inhibitors of human NE (Merck Research Laboratories, Kenilworth, NJ, USA), focusing on 1 inhibitor called MK0339, a potent, orally absorbed agent that had been tested in clinical trials and shown to have a favorable safety profile. Because fresh, primary bone marrow cells are rarely available in sufficient quantities for research studies, we used 3 cellular models: patient-derived, induced pluripotent stem cells (iPSCs); HL60 cells transiently expressing mutant NE; and HL60 cells with regulated expression of the mutant enzyme. In all 3 models, the cells expressing the mutant enzyme had reduced survival as measured with annexin V and FACS. Coincubation with the inhibitors, particularly MK0339, promoted cell survival and increased formation of mature neutrophils. These studies suggest that cell-permeable inhibitors of neutrophil elastase show promise as novel therapies for ELANE-associated neutropenia.

How I manage children with neutropenia

Neutropenia, usually defined as a blood neutrophil count <1·5 × 10⁹ /l, is a common medical problem for children and adults. There are many causes for neutropenia, and at each stage in life the clinical pattern of causes and consequences differs significantly. I recommend utilizing the age of the child and clinical observations for the preliminary diagnosis and primary management. In premature infants, neutropenia is quite common and contributes to the risk of sepsis with necrotizing enterocolitis. At birth and for the first few months of life, neutropenia is often attributable to isoimmune or alloimmune mechanisms and predisposes to the risk of severe bacterial infections. Thereafter when a child is discovered to have neutropenia, often associated with relatively minor symptoms, it is usually attributed to autoimmune disorder or viral infection. The congenital neutropenia syndromes are usually recognized when there are recurrent infections, the neutropenia is severe and there are congenital anomalies suggesting a genetic disorder. This review focuses on the key clinical finding and laboratory tests for diagnosis with commentaries on treatment, particularly the use of granulocyte colony-stimulating factor to treat childhood neutropenia.

Autoimmune and other acquired neutropenias

This educational review addresses the diagnostic evaluation of patients for autoimmune and other forms of acquired neutropenia, including the futility of deconstructing the overlap of chronic "autoimmune," "benign," and "idiopathic" categories. Isolated neutropenias caused by infection, drugs, and immunologic disorders are also addressed. Discussion of management options emphasizes a conservative approach, with largely supportive care for these mostly benign and self-limited disorders.