The PARN, TOE1, and USB1 RNA deadenylases and their roles in non-coding RNA regulation.

The levels of non-coding RNAs (ncRNAs) are regulated by transcription, RNA processing, and RNA degradation pathways. One mechanism for the degradation of ncRNAs involves the addition of oligo(A) tails by non-canonical poly(A) polymerases, which then recruit processive sequence-independent 3' to 5' exonucleases for RNA degradation. This pathway of decay is also regulated by three 3' to 5' exoribonucleases, USB1, PARN, and TOE1, which remove oligo(A) tails and thereby can protect ncRNAs from decay in a manner analogous to the deubiquitination of proteins. Loss-of-function mutations in these genes lead to premature degradation of some ncRNAs and lead to specific human diseases such as Poikiloderma with Neutropenia (PN) for USB1, Dyskeratosis Congenita (DC) for PARN and Pontocerebellar Hypoplasia type 7 (PCH7) for TOE1. Herein, we review the biochemical properties of USB1, PARN, and TOE1, how they modulate ncRNA levels, and their roles in human diseases.

Impaired myelopoiesis in congenital neutropenia: insights into clonal and malignant hematopoiesis.

A common feature of both congenital and acquired forms of bone marrow failure is an increased risk of developing acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Indeed, the development of MDS or AML is now the major cause of mortality in patients with congenital neutropenia. Thus, there is a pressing clinical need to develop better strategies to prevent, diagnose early, and treat MDS/AML in patients with congenital neutropenia and other bone marrow failure syndromes. Here, we discuss recent data characterizing clonal hematopoiesis and progression to myeloid malignancy in congenital neutropenia, focusing on severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome. We summarize recent studies showing excellent outcomes after allogenic hematopoietic stem cell transplantation for many (but not all) patients with congenital neutropenia, including patients with SCN with active myeloid malignancy who underwent transplantation. Finally, we discuss how these new data inform the current clinical management of patients with congenital neutropenia.

Diagnosis and therapeutic decision-making for the neutropenic patient.

Determining the cause of a low neutrophil count in a pediatric or adult patient is essential for the hematologist's clinical decision-making. Fundamental to this diagnostic process is establishing the presence or lack of a mature neutrophil storage pool, as absence places the patient at higher risk for infection and the need for supportive care measures. Many diagnostic tests, eg, a peripheral blood smear and bone marrow biopsy, remain important tools, but greater understanding of the diversity of neutropenic disorders has added new emphasis on evaluating for immune disorders and genetic testing. In this article, a structure is provided to assess patients based on the mechanism of neutropenia and to prioritize testing based on patient age and hypothesized pathophysiology. Common medical quandaries including fever management, need for growth factor support, risk of malignant transformation, and curative options in congenital neutropenia are reviewed to guide medical decision-making in neutropenic patients.

Hyperbaric oxygen management of recurrent cellulitis in poikiloderma with neutropenia.

Poikiloderma with neutropenia (PN), is a rare autosomal recessive condition with many associated complications and manifestations. Here we present a patient with confirmed PN who is of one-quarter Chucktaw or Cherokee heritage with no known descent from the Navajo tribe. The patient's condition was complicated by chronic bilateral lower limb cellulitis and associated osteomyelitis which was unresponsive to extensive antibiotic regimens. Subsequent treatment with hyperbaric oxygen therapy (HBOT) was successful. To date, no author has reported on the treatment of recurrent cellulitis using HBOT in this patient population. Based on our experience, HBOT should be considered in patients with PN.

Childhood Sjögren syndrome: features of an international cohort and application of the 2016 ACR/EULAR classification criteria.

OBJECTIVE: Sjögren syndrome in children is a poorly understood autoimmune disease. We aimed to describe the clinical and diagnostic features of children diagnosed with Sjögren syndrome and explore how the 2016 ACR/EULAR classification criteria apply to this population. METHODS: An international workgroup retrospectively collected cases of Sjögren syndrome diagnosed under 18 years of age from 23 centres across eight nations. We analysed patterns of symptoms, diagnostic workup, and applied the 2016 ACR/EULAR classification criteria. RESULTS: We identified 300 children with Sjögren syndrome. The majority of patients n = 232 (77%) did not meet 2016 ACR/EULAR classification criteria, but n = 110 (37%) did not have sufficient testing done to even possibly achieve the score necessary to meet criteria. Even among those children with all criteria items tested, only 36% met criteria. The most common non-sicca symptoms were arthralgia [n = 161 (54%)] and parotitis [n = 140 (47%)] with parotitis inversely correlating with age. CONCLUSION: Sjögren syndrome in children can present at any age. Recurrent or persistent parotitis and arthralgias are common symptoms that should prompt clinicians to consider the possibility of Sjögren syndrome. The majority of children diagnosed with Sjögren syndromes did not meet 2016 ACR/EULAR classification criteria. Comprehensive diagnostic testing from the 2016 ACR/EULAR criteria are not universally performed. This may lead to under-recognition and emphasizes a need for further research including creation of paediatric-specific classification criteria.

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 year olds, 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.

Association Between Depth of Neutropenia and Clinical Outcomes in Febrile Pediatric Cancer and/or Patients Undergoing Hematopoietic Stem-cell Transplantation.

BACKGROUND: Infectious Diseases Society of America guidelines defines febrile neutropenia (FN) patients as high risk, if they have an absolute neutrophil count (ANC) ≤100 cells/µL anticipated to last >7 days. However, data evaluating the clinical significance of the depth and duration of neutropenia are limited. METHODS: We conducted a retrospective cohort study of pediatric oncology patients presenting with FN to examine whether the effects of the depth and duration of neutropenia prior to presentation were predictive of blood stream infection (BSI), invasive fungal disease (IFD), pediatric intensive care unit (PICU) admission or length of stay. RESULTS: A total of 585 FN episodes (FNEs) were identified in 265 patients. ANC at the time of presentation was <100 in 411 (70%), 100-500 in 119 (20%), and >500 cells/µL with subsequent decline to <500 cells/µL in the next 48 hours in 55 (10%) of FNEs. In the group with ANC > 500 with subsequent decline in 48 hours, rates of IFD and BSI were higher when compared with ANC < 100 cells/µL [odds ratio (OR) = 5.9, 95% confidence interval (CI): 0.7-29.6] and (OR = 2.35, 95% CI: 01.02-5.4), and patients in this group were more likely to be admitted to the PICU (OR= 5.1, 95% CI: 1.134-19.46). No difference in outcomes was identified when the groups of ANC < 100 and ANC of 100-500 cells/µL were compared. Neutropenia >7 days prior to FNE was an independent risk factor for BSI (OR = 2.88, 95% CI: 1.55-5.35 and increased length of stay. CONCLUSIONS: Clinicians should not be reassured when patients present with FN and initial ANC >500 cells/mL after recent chemotherapy if continued decline is expected as patients in this group are at high risk of IFD, BSI and PICU admission.

Two monogenic disorders masquerading as one: severe congenital neutropenia with monocytosis and non-syndromic sensorineural hearing loss.

BACKGROUND: We report a large family with four successive generations, presenting with a complex phenotype of severe congenital neutropenia (SCN), partially penetrant monocytosis, and hearing loss of varying severity. METHODS: We performed whole exome sequencing to identify the causative variants. Sanger sequencing was used to perform segregation analyses on remaining family members. RESULTS: We identified and classified a pathogenic GFI1 variant and a likely pathogenic variant in MYO6 which together explain the complex phenotypes seen in this family. CONCLUSIONS: We present a case illustrating the benefits of a broad screening approach that allows identification of oligogenic determinants of complex human phenotypes which may have been missed if the screening was limited to a targeted gene panel with the assumption of a syndromic disorder. This is important for correct genetic diagnosis of families and disentangling the range and severity of phenotypes associated with high impact variants.

Impact of genotype on neutropenia in a large cohort of Serbian patients with glycogen storage disease type Ib.

BACKGROUND: Glycogen storage disease type Ib (GSD-Ib) is an inherited metabolic disorder caused by autosomal recessive mutations in SLC37A4 coding for the glucose-6-phosphate transporter. Neutropenia represents major feature of GSD-Ib along with metabolic disturbances. Previous research in GSD-Ib patients did not reveal significant genotype-phenotype correlation. Our objective was to explore the frequency and severity of neutropenia and it's complications in relation to genotype of GSD-Ib patients. METHODS: We estimated cumulative incidence of neutropenia and severe neutropenia, relation of genotype to absolute neutrophil count (ANC), and dynamics of ANC during serious bacterial infections (SBI) in a cohort of Serbian GSD Ib patients. Impact of genotype on GSD Ib-related inflammatory bowel disease (IBD) was also assessed. RESULTS: Absolute neutrophil count (ANC) < 1500/mm3 was present in all 33 patients, with severe neutropenia (ANC<500/mm3) occurring in 60.6% of patients. The median age at neutropenia onset was 24 months, while severe neutropenia developed at median of 4.5 years. The ANC was elevated during 90.5% episodes of SBI. Genotypes c.81T>A/c.785G>A and c.81T>A/c.1042_1043delCT are associated with earlier onset of neutropenia. Patients carrying c.785G>A mutation express a higher capacity for ANC increase during SBI. Inflammatory bowel disease was diagnosed in 8 patients (24.2% of total) with median age of onset at 7 years. Risk for IBD occurrence was not significantly affected by gender, genotype and severity of neutropenia. CONCLUSIONS: We may conclude that certain mutations in SLC37A4 influence the risk for severe neutropenia occurrence but also affect the capacity to increase ANC during SBI.

Neutrophils in community-acquired pneumonia: parallels in dysfunction at the extremes of age.

"Science means constantly walking a tight rope" Heinrich Rohrer, physicist, 1933. Community-acquired pneumonia (CAP) is the leading cause of death from infectious disease worldwide and disproportionately affects older adults and children. In high-income countries, pneumonia is one of the most common reasons for hospitalisation and (when recurrent) is associated with a risk of developing chronic pulmonary conditions in adulthood. Pneumococcal pneumonia is particularly prevalent in older adults, and here, pneumonia is still associated with significant mortality despite the widespread use of pneumococcal vaccination in middleand high-income countries and a low prevalence of resistant organisms. In older adults, 11% of pneumonia survivors are readmitted within months of discharge, often with a further pneumonia episode and with worse outcomes. In children, recurrent pneumonia occurs in approximately 10% of survivors and therefore is a significant cause of healthcare use. Current antibiotic trials focus on short-term outcomes and increasingly shorter courses of antibiotic therapy. However, the high requirement for further treatment for recurrent pneumonia questions the effectiveness of current strategies, and there is increasing global concern about our reliance on antibiotics to treat infections. Novel therapeutic targets and approaches are needed to improve outcomes. Neutrophils are the most abundant immune cell and among the first responders to infection. Appropriate neutrophil responses are crucial to host defence, as evidenced by the poor outcomes seen in neutropenia. Neutrophils from older adults appear to be dysfunctional, displaying a reduced ability to target infected or inflamed tissue, poor phagocytic responses and a reduced capacity to release neutrophil extracellular traps (NETs); this occurs in health, but responses are further diminished during infection and particularly during sepsis, where a reduced response to granulocyte colony-stimulating factor (G-CSF) inhibits the release of immature neutrophils from the bone marrow. Of note, neutrophil responses are similar in preterm infants. Here, the storage pool is decreased, neutrophils are less able to degranulate, have a reduced migratory capacity and are less able to release NETs. Less is known about neutrophil function from older children, but theoretically, impaired functions might increase susceptibility to infections. Targeting these blunted responses may offer a new paradigm for treating CAP, but modifying neutrophil behaviour is challenging; reducing their numbers or inhibiting their function is associated with poor clinical outcomes from infection. Uncontrolled activation and degranulation can cause significant host tissue damage. Any neutrophil-based intervention must walk the tightrope described by Heinrich Rohrer, facilitating necessary phagocytic functions while preventing bystander host damage, and this is a significant challenge which this review will explore.

Variability in body temperature in healthy adults and in patients receiving chemotherapy: prospective observational cohort study.

Between-individual variability of body temperature has been little investigated, but is of clinical importance: for example, in detection of neutropenic sepsis during chemotherapy. We studied within-person and between-person variability in temperature in healthy adults and those receiving chemotherapy using a prospective observational design involving 29 healthy participants and 23 patients undergoing chemotherapy. Primary outcome was oral temperature. We calculated each patient's mean temperature, standard deviation within each patient (within-person variability), and between patients (between-person variability). Secondary analysis explored temperature changes in the three days before admission for neutropenic sepsis. 1,755 temperature readings were returned by healthy participants and 1,765 by chemotherapy patients. Mean participant temperature was 36.16 C (95% CI 36.07-36.26) in healthy participants and 36.32 C (95% CI 36.18-36.46) in chemotherapy patients. Healthy participant within-person variability was 0.40 C (95% CI 0.36-0.44) and between-person variability was 0.26 C (95% CI 0.16-0.35). Chemotherapy patient within-person variability was 0.39 C (95% CI 0.34-0.44) and between-person variability was 0.34 C (95% CI 0.26-0.48). Thus, use of a population mean rather than personalised baselines is probably sufficient for most clinical purposes as between-person variability is not large compared to within-person variability. Standardised guidance and provision of thermometers to patients might help to improve recording and guide management.

Oncologic Emergencies: The Fever With Too Few Neutrophils.

BACKGROUND: Cancer is associated with a variety of complications, including neutropenic fever, which can result in severe morbidity and mortality. This oncologic emergency requires ED management. OBJECTIVE: This narrative review provides focused updates for emergency clinicians regarding neutropenic fever. DISCUSSION: Neutropenic fever is defined by fever with oral temperature >38.3°C or temperature >38.0°C for 1 hour with an absolute neutrophil count (ANC) < 1000 cells/microL. Patients who have received chemotherapy within 6 weeks of presentation are at high risk for neutropenia. While most patients with neutropenic fever do not have an identifiable bacterial source of fever, clinicians should treat patients for bacterial infection. Rapid assessment and management are vital to improving outcomes in patients with suspected or confirmed neutropenic fever. History and examination should focus on the most common sites of infection: the gastrointestinal tract, blood, skin, lung, and urinary tract. However, physical examination and laboratory or imaging assessment may not display classic signs of infection. Blood cultures should be obtained, and broad-spectrum antibiotics are recommended. Oncology consultation is an integral component in the care of these patients. Several risk scores can assist in stratifying patients who may be appropriate for discharge home and follow-up. CONCLUSIONS: Neutropenic fever is an oncologic emergency. Rapid diagnosis and care of patients with neutropenic fever can improve outcomes, along with oncology consultation.

Temperatures and blood counts in pediatric patients treated with chemotherapy for cancer, NCT01683370.

Fever in neutropenia (FN) is the most frequent potentially lethal complication of chemotherapy in patients with cancer. The temperature limit defining fever (TLDF) for FN is based on scarce evidence. This prospective, single center observational study recruited non-selected pediatric patients diagnosed with cancer between ≥1 and ≤17 years in 2012 and 2013. Of 40 patients potentially eligible, 39 participated. Data of 8896 temperature measurements and 1873 complete blood counts (CBCs) were recorded over 289 months (24.1 years) of chemotherapy exposure time. During this time 43 FN episodes were diagnosed. In 32 episodes, FN diagnosis was based on reaching the local (i.e. Bern, Switzerland) standard TLDF of 39.0 °C; another 11 episodes had been captured by clinical judgement (i.e. temperature < 39.0 °C). These data can be used to simulate the effects of various TLDFs on the rate of FN diagnosis. We assume merging these data with other data sets is feasible.

Response of an oscillatory differential delay equation to a periodic stimulus.

Periodic hematological diseases such as cyclical neutropenia or cyclical thrombocytopenia, with their characteristic oscillations of circulating neutrophils or platelets, may pose grave problems for patients. Likewise, periodically administered chemotherapy has the unintended side effect of establishing periodic fluctuations in circulating white cells, red cell precursors and/or platelets. These fluctuations, either spontaneous or induced, often have serious consequences for the patient (e.g. neutropenia, anemia, or thrombocytopenia respectively) which exogenously administered cytokines can partially correct. The question of when and how to administer these drugs is a difficult one for clinicians and not easily answered. In this paper we use a simple model consisting of a delay differential equation with a piecewise linear nonlinearity, that has a periodic solution, to model the effect of a periodic disease or periodic chemotherapy. We then examine the response of this toy model to both single and periodic perturbations, meant to mimic the drug administration, as a function of the drug dose and the duration and frequency of its administration to best determine how to avoid side effects.

Episodes of fever in neutropenia in pediatric patients with cancer in Bern, Switzerland, 1993-2012.

Fever in neutropenia (FN) is the most frequent potentially life threatening complication of chemotherapy for cancer. Prediction of the risk to develop complications, integrated into clinical decision rules, would allow for risk-stratified treatment of FN. This retrospective, single center cohort study in pediatric patients diagnosed with cancer before 17 years, covered two decades, 1993 to 2012. In total, 703 FN episodes in 291 patients with chemotherapy (maximum per patient, 9) were reported here. Twenty-nine characteristics of FN were collected: 6 were patient- and cancer-related, 8 were characteristics of history, 8 of clinical examination, and 7 laboratory results in peripheral blood, all known at FN diagnosis. In total 28 FN outcomes were assessed: 8 described treatment of FN, 6 described microbiologically defined infections (MDI), 4 clinically defined infections, 4 were additional clinical composite outcomes, and 6 outcomes were related to discharge. These data can mainly be used to study FN characteristics and their association with outcomes over time and between centers, and for derivation and external validation of clinical decision rules.

Mutation, drift and selection in single-driver hematologic malignancy: Example of secondary myelodysplastic syndrome following treatment of inherited neutropenia.

Cancer development is driven by series of events involving mutations, which may become fixed in a tumor via genetic drift and selection. This process usually includes a limited number of driver (advantageous) mutations and a greater number of passenger (neutral or mildly deleterious) mutations. We focus on a real-world leukemia model evolving on the background of a germline mutation. Severe congenital neutropenia (SCN) evolves to secondary myelodysplastic syndrome (sMDS) and/or secondary acute myeloid leukemia (sAML) in 30-40%. The majority of SCN cases are due to a germline ELANE mutation. Acquired mutations in CSF3R occur in >70% sMDS/sAML associated with SCN. Hypotheses underlying our model are: an ELANE mutation causes SCN; CSF3R mutations occur spontaneously at a low rate; in fetal life, hematopoietic stem and progenitor cells expands quickly, resulting in a high probability of several tens to several hundreds of cells with CSF3R truncation mutations; therapeutic granulocyte colony-stimulating factor (G-CSF) administration early in life exerts a strong selective pressure, providing mutants with a growth advantage. Applying population genetics theory, we propose a novel two-phase model of disease development from SCN to sMDS. In Phase 1, hematopoietic tissues expand and produce tens to hundreds of stem cells with the CSF3R truncation mutation. Phase 2 occurs postnatally through adult stages with bone marrow production of granulocyte precursors and positive selection of mutants due to chronic G-CSF therapy to reverse the severe neutropenia. We predict the existence of the pool of cells with the mutated truncated receptor before G-CSF treatment begins. The model does not require increase in mutation rate under G-CSF treatment and agrees with age distribution of sMDS onset and clinical sequencing data.

Zebrafish Granulocyte Colony-Stimulating Factor Receptor Maintains Neutrophil Number and Function throughout the Life Span.

Granulocyte colony-stimulating factor receptor (G-CSFR), encoded by the CSF3R gene, represents a major regulator of neutrophil production and function in mammals, with inactivating extracellular mutations identified in a cohort of neutropenia patients unresponsive to G-CSF treatment. This study sought to elucidate the role of the zebrafish G-CSFR by generating mutants harboring these inactivating extracellular mutations using genome editing. Zebrafish csf3r mutants possessed significantly decreased numbers of neutrophils from embryonic to adult stages, which were also functionally compromised, did not respond to G-CSF, and displayed enhanced susceptibility to bacterial infection. The study has identified an important role for the zebrafish G-CSFR in maintaining the number and functionality of neutrophils throughout the life span and created a bona fide zebrafish model of nonresponsive neutropenia.