Bone marrow granulocyte reserve in chronic benign idiopathic neutropenia

Discerning clinicopathological features of congenital neutropenia syndromes: an approach to diagnostically challenging differential diagnoses

The congenital neutropenia syndromes are rare haematological conditions defined by impaired myeloid precursor differentiation or function. Patients are prone to severe infections with high mortality rates in early life. While some patients benefit from granulocyte colony-stimulating factor treatment, they may still face an increased risk of bone marrow failure, myelodysplastic syndrome and acute leukaemia. Accurate diagnosis is crucial for improved outcomes; however, diagnosis depends on familiarity with a heterogeneous group of rare disorders that remain incompletely characterised. The clinical and pathological overlap between reactive conditions, primary and congenital neutropenias, bone marrow failure, and myelodysplastic syndromes further clouds diagnostic clarity.We review the diagnostically useful clinicopathological and morphological features of reactive causes of neutropenia and the most common primary neutropenia disorders: constitutional/benign ethnic neutropenia, chronic idiopathic neutropenia, cyclic neutropenia, severe congenital neutropenia (due to mutations in ELANE, GFI1, HAX1, G6PC3, VPS45, JAGN1, CSF3R, SRP54, CLPB and WAS), GATA2 deficiency, Warts, hypogammaglobulinaemia, infections and myelokathexis syndrome, Shwachman-Diamond Syndrome, the lysosomal storage disorders with neutropenia: Chediak-Higashi, Hermansky-Pudlak, and Griscelli syndromes, Cohen, and Barth syndromes. We also detail characteristic cytogenetic and molecular factors at diagnosis and in progression to myelodysplastic syndrome/leukaemia.

Clozapine haematological monitoring for neutropenia: a global perspective

AIMS

Clozapine is licensed for treatment-resistant psychosis and remains underutilised. This may berelated to the stringent haematological monitoring requirements that are mandatory in most countries. We aimed to compare guidelines internationally and develop a novel Stringency Index. We hypothesised that the most stringent countries would have increased healthcare costs and reduced prescription rates.

METHOD

We conducted a literature review and survey of guidelines internationally. Guideline identification involved a literature review and consultation with clinical academics. We focused on the haematological monitoring parameters, frequency and thresholds for discontinuation and rechallenge after suspected clozapine-induced neutropenia. In addition, indicators reflecting monitoring guideline stringency were scored and visualised using a choropleth map. We developed a Stringency Index with an international panel of clozapine experts, through a modified-Delphi-survey. The Stringency Index was compared to health expenditure per-capita and clozapine prescription per 100 000 persons.

RESULTS

One hundred twocountries were included, from Europe (n = 35), Asia (n = 24), Africa (n = 20), South America (n = 11), North America (n = 7) and Oceania and Australia (n = 5). Guidelines differed in frequency of haematological monitoring and discontinuation thresholds. Overall, 5% of included countries had explicit guidelines for clozapine-rechallenge and 40% explicitly prohibited clozapine-rechallenge. Furthermore, 7% of included countries had modified discontinuation thresholds for benign ethnic neutropenia. None of the guidelines specified how long haematological monitoring should continue. The most stringent guidelines were in Europe, and the least stringent were in Africa and South America. There was a positive association (r = 0.43, p < 0.001) between a country's Stringency Index and healthcare expenditure per capita.

CONCLUSIONS

Recommendations on how haematological function should be monitored in patients treated with clozapine vary considerably between countries. It would be useful to standardise guidelines on haematological monitoring worldwide.

Benign ethnic neutropenia: an analysis of prevalence, timing and identification accuracy in two large inner-city NHS hospitals

BACKGROUND

Benign ethnic neutropenia (BEN) is the most common cause of chronic neutropenia seen in individuals of African, Middle Eastern and West Indian descent. This phenotype is broadly defined by an absolute neutrophil counts (ANC) below 1.8 × 10⁹ cells/L in the absence of other causes, without an increased risk of infection. BEN has been implicated as a potential source of disparity in patients treated with clozapine, the antipsychotic of choice in treatment-resistant schizophrenia. Our main objective was to examine the current level of BEN recognition in a cohort of patients treated with clozapine and the potential impact of unidentified BEN on the initiation and maintenance of clozapine treatment.

METHODS

This was an observational, retrospective analysis of patients registered with clozapine haematological monitoring systems in two large mental health trusts, chosen because they serve an ethnically diverse population. The first objective was to establish certified BEN prevalence in current users of clozapine. The second objective was to explore the stage of treatment at which BEN was identified. The third objective was to evaluate the extent of unrecognised BEN in patients registered on the Central Non-Rechallenge Database (CNRD), a database for patients whose haematological parameters fall below set thresholds when receiving clozapine treatment, meaning they cannot ordinarily be prescribed clozapine again.

RESULTS

The study population comprised of 2020 patients on the clozapine register. 111 patients were monitored under BEN criteria. BEN was mostly identified after a below threshold haematological result or clozapine rechallenge (68%) compared to at clozapine initiation (32%). Eight of the 18 (42%) black patients registered on the CNRD were classified as BEN after assessment by a haematologist. Of these 8 patients, none would have met CNRD criteria again if monitored with BEN criteria at clozapine initiation.

CONCLUSIONS

Current evidence suggests that BEN remains an uncommonly recognised haematological phenotype. Improved timely identification of BEN will reduce unnecessary interruption or discontinuation of clozapine treatment. Our results suggest consideration should also be given to determining BEN status prior to initiating clozapine. Moreover, adoption of current FDA BEN monitoring criteria in the UK may further reduce clozapine discontinuation due to perceived neutropenia as drug toxicity, particularly in treatment-refractory schizophrenia patients.

Awan Z, Abouzaid AA, Elbahaie HM, Al Amoudi SM, Andarawi M, F Shehata S. The Prevalence of Isolated Neutropenia at High Altitude in Southern Saudi Arabia: Does Altitude Affect Leucocyte Count?

INTRODUCTION

Isolated neutropenia is a common problem in hematology practice. Benign ethnic neutropenia (BEN) is the common form of neutropenia worldwide and it affects mainly African and Middle Eastern ethnicities. Most cases of isolated mild and moderate neutropenia are benign and associated with no clinical significance. The aim of this study was to estimate the prevalence of isolated neutropenia at high-altitude southern Saudi Arabia.

METHODS

A large dataset of complete blood counts (CBCs) was analyzed for walk-in patients of both genders, of age ranges from 12 to 60 years doing blood tests at a commercial lab for high altitude - 2,270 meters above sea level - (HA) group, and from sea level SL group. Abnormal biochemical or CBC results were excluded before analysis.

RESULTS

For HA group, 3123 CBCs were analyzed and for SL group 18,427 CBCs were analyzed. The prevalence of mild neutropenia, defined as absolute neutrophil count (ANC) in the range of 1.0-.5× 109/L, was 12.4% (n=399) versus 5.6% (n=1025), while moderate neutropenia, defined as ANC of 0.5-1 × 109/L, was present 6% (n=191) versus 1.45% (n=269) in the high altitude and sea level groups, respectively. Severe neutropenia, defined as neutrophil count less than 0.5-1 × 109/L, was rare in both groups.

CONCLUSION

Isolated neutropenia is common in Saudis living at high altitude. While benign ethnic neutropenia (BEN) is thought to be the major contributing factor to this high prevalence, other factors including environmental factors and altitude are possible contributing factors along with underlying ethnic neutropenia.

Benign ethnic neutropenia

Benign ethnic neutropenia (BEN) is one of the most common causes of chronic neutropenia seen in individuals of African, Middle Eastern and West Indian descent, affecting many individuals worldwide. Despite its prevalence, many physicians are not familiar with this benign condition, resulting in unnecessary evaluation and testing for neutropenia in otherwise healthy individuals. Clinically, patients with BEN are at no increased risk of infection despite their neutropenia. Implications of this condition are highlighted in those patients receiving therapies that have a known side effect of neutropenia, most commonly chemotherapy agents. Studies have suggested that disparities in survival among those patients receiving chemotherapy between patients of European decent and African decent may be attributed to measured neutropenia in these populations, questioning whether BEN could be an influential factor. This review encompasses all aspects of benign ethnic neutropenia, providing information about this condition and helping to guide clinical decision-making as to when an aggressive work up and referral are indicated and when it is appropriate to monitor. Additionally, we review the role of genetic studies in identifying the genes related to BEN, summarize the theories that offer the most accepted mechanisms behind the condition, and address the importance of pursuing larger studies to assess the implication of BEN in oncology patients as well as patients taking neutropenia-causing medications.

Identification and Clinical Characterization of Children With Benign Ethnic Neutropenia

Benign ethnic neutropenia (BEN) is an asymptomatic condition reported in adults of African and Middle Eastern descent. The clinical description in children is currently lacking. In our urban outpatient pediatric hematology clinic, the median neutrophil count of children with BEN was lower than previous reports in adults at 893×10 cells/L, but increased with older age. There was an equal male to female ratio and 24% of our BEN children reported ethnicities other than African or Middle Eastern. Children with BEN had a clinical course comparable with other healthy children including otherwise normal blood counts, except for mild anemia.

Lymphocyte subsets in healthy adult Kuwaiti Arabs with relative benign ethnic neutropenia

Relative and absolute neutropenia is frequently seen in the healthy adult Kuwaiti Arab population. Fluorescent monoclonal antibody labelling followed by flow cytometry was used to determine the lymphocyte subsets in 48 normal healthy individuals in the Kuwaiti adult population (24 males and 24 females, age 17-59 years) with relative or absolute neutropenia, and this was compared to age-matched controls (64 males and 63 females). The mean haemoglobin levels were 13.6+/-1.5 and 13.7+/-1.5 g/dl in the neutropenic and control groups, respectively. White blood cell counts, absolute neutrophil and lymphocyte counts in neutropenic individuals with the corresponding reference range, taken from the control subjects (in parenthesis) were: WBC, 6.7+/-1.6 x 10(9)/l (4-10.4 x 10(9)/l), neutrophils, 2.7+/-0.8 x 10(9)/l (1.87-6.63 x 10(9)/l), lymphocytes, 3.3+/-0.9 x 10(9)/l (1.4-3.62 x 10(9)/l). Absolute values of lymphocytes, CD2+, CD3+, CD19+, CD4+, CD8+, HLADR+ and CD45RA+ cells were significantly higher in the neutropenic group. The range of values with the corresponding reference ranges, in parenthesis, were: CD2+, 1.61-4.30 x 10(9)/l (0.95-2.99 x 10(9)/l), CD3+, 1.37-4.16 x 10(9)/l (0.83-2.71 x 10(9)/l), CD19+, 0.16-1.09 x 10(9)/l (0.05-0.61 x 10(9)/l), CD4+, 0.70-2.89 x 10(9)/l (0.45-1.65 x 10(9)/l), CD8+, 0.57-1.80 x 10(9)/l (0.29-1.17 x 10(9)/l), HLADR+ 0.27-1.74 x 10(9)/l (0.02-0.62 x 10(9)/l), CD45RA, 0.90-4.63 x 10(9)/l (0.34-2.05 x 10(9)/l), respectively. The levels of natural killer cells, CD56+ cells were significantly lower compared to controls while the values of memory T lymphocytes, CD45RO+ were comparable to controls. These results indicate that difference in the leukocyte subpopulations may also be indicative of differences in the lymphocyte subpopulations and that reference ranges for these cell types in healthy neutropenic and non-neutropenic individuals should be established.

Idiopathic, immune, infectious, and idiosyncratic neutropenias

In idiopathic and immune neutropenias the susceptibility to infectious agents is highly variable, but the reason why some patients exhibit no undue susceptibility whereas others contract life-threatening infections is poorly understood. An important factor is the efficacy of delivery of neutrophils to the tissues. Recent investigations of the mechanisms for mild to moderate chronic neutropenias have shown the significance of interactions between myelopoiesis and the immune system, as for example, in relation to immunoglobulin aberrations and the cytokine network. Antibody-mediated neutropenias (alloimmune, autoimmune) are now well-characterized diseases. If infections occur, apart from antibiotics, granulocyte colony-stimulating factor (G-CSF) is the treatment of choice, while intravenous or monoclonal immunoglobulins and cyclosporine are reserved for refractory cases.

Benign ethnic neutropenia: what is a normal absolute neutrophil count?

Approximately 25% to 50% of persons of African descent and some ethnic groups in the Middle East have benign ethnic neutropenia, with low leukocyte and neutrophil counts. It is important to recognize the existence of this condition, the most common form of neutropenia throughout the world, and thus avoid both under-and overevaluation. Although there is no scientific basis for an absolute neutrophil count of 1.5x10(9)/L to be considered minimal, counts below this level are empirically regarded as inadequate in persons of all ethnic groups who are above the age of 1 year. Many individuals, however, maintain consistently low absolute neutrophil counts without evidence of increased susceptibility to infection or any other adverse effect. The important determination is not how many neutrophils are present in the peripheral blood, but whether the bone marrow is able to produce enough normally functioning cells when needed. A description of benign ethnic neutropenia, as set forth in this review, suggests that the lower limit now considered acceptable for the absolute neutrophil count should be readjusted downward for all ethnic groups.