First described in 1983, Barth syndrome (BTHS) is widely regarded as a rare X-linked genetic disease characterised by cardiomyopathy (CM), skeletal myopathy, growth delay, neutropenia and increased urinary excretion of 3-methylglutaconic acid (3-MGCA). Fewer than 200 living males are known worldwide, but evidence is accumulating that the disorder is substantially under-diagnosed. Clinical features include variable combinations of the following wide spectrum: dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), endocardial fibroelastosis (EFE), left ventricular non-compaction (LVNC), ventricular arrhythmia, sudden cardiac death, prolonged QTc interval, delayed motor milestones, proximal myopathy, lethargy and fatigue, neutropenia (absent to severe; persistent, intermittent or perfectly cyclical), compensatory monocytosis, recurrent bacterial infection, hypoglycaemia, lactic acidosis, growth and pubertal delay, feeding problems, failure to thrive, episodic diarrhoea, characteristic facies, and X-linked family history. Historically regarded as a cardiac disease, BTHS is now considered a multi-system disorder which may be first seen by many different specialists or generalists. Phenotypic breadth and variability present a major challenge to the diagnostician: some children with BTHS have never been neutropenic, whereas others lack increased 3-MGCA and a minority has occult or absent CM. Furthermore, BTHS was first described in 2010 as an unrecognised cause of fetal death. Disabling mutations or deletions of the tafazzin (TAZ) gene, located at Xq28, cause the disorder by reducing remodeling of cardiolipin, a principal phospholipid of the inner mitochondrial membrane. A definitive biochemical test, based on detecting abnormal ratios of different cardiolipin species, was first described in 2008. Key areas of differential diagnosis include metabolic and viral cardiomyopathies, mitochondrial diseases, and many causes of neutropenia and recurrent male miscarriage and stillbirth. Cardiolipin testing and TAZ sequencing now provide relatively rapid diagnostic testing, both prospectively and retrospectively, from a range of fresh or stored tissues, blood or neonatal bloodspots. TAZ sequencing also allows female carrier detection and antenatal screening. Management of BTHS includes medical therapy of CM, cardiac transplantation (in 14% of patients), antibiotic prophylaxis and granulocyte colony-stimulating factor (G-CSF) therapy. Multidisciplinary teams/clinics are essential for minimising hospital attendances and allowing many more individuals with BTHS to live into adulthood.

Neutrophils are vital in defence against pathogens, but excessive neutrophil activity can lead to tissue damage and promote acute respiratory distress syndrome. COVID-19 is associated with systemic expansion of immature neutrophils, but the functional consequences of this shift to immaturity are not understood. We used flow cytometry to investigate activity and phenotypic diversity of circulating neutrophils in acute and convalescent COVID-19 patients. First, we demonstrate hyperactivation of immature CD10−subpopulations in severe disease, with elevated markers of secondary granule release. Partially activated immature neutrophils were detectable 12 wk post-hospitalisation, indicating long term myeloid dysregulation in convalescent COVID-19 patients. Second, we demonstrate that neutrophils from moderately ill patients down-regulate the chemokine receptor CXCR2, whereas neutrophils from severely ill individuals fail to do so, suggesting an altered ability for organ trafficking and a potential mechanism for induction of disease tolerance. CD10−and CXCR2hineutrophil subpopulations were enriched in severe disease and may represent prognostic biomarkers for the identification of individuals at high risk of progressing to severe COVID-19.

Purpose of the review Barth syndrome is an X-linked disease characterised by defective remodelling of phospholipid side chains in mitochondrial membranes. Major features include neutropenia, dilated cardiomyopathy, motor delay and proximal myopathy, feeding problems and constitutional growth delay. We conducted this review of neutropenia in Barth syndrome to aid in the diagnosis of this disease, and to improve understanding of both the consequences of neutropenia and the benefits of treatment with granulocyte colony-stimulating factor (G-CSF). Recent findings In 88 patients with Barth syndrome, neutropenia, i.e. at least one count below 1.5 × 109/L, was detected in 74 (84%) and 44% had severe chronic neutropenia, with multiple counts below 0.5 × 109/L. The pattern of neutropenia varied between intermittent and unpredictable, chronic and severe, or cyclical with mathematically regular oscillations. Monocytosis, i.e., monocytes >1.0 × 109/L, was observed at least once in 64 of 85 (75%) patients. Granulocyte colony stimulating factor (G-CSF) was administered to 39 of 88 subjects (44%). Weekly average G-CSF doses ranged from 0.12 to 10.92 mcg/kg/day (mean 1.16 mcg/kg/day, median 1.16 mcg/kg/day). Antibiotic prophylaxis was additionally employed in 21 of 26 neutropenic patients. Pre-treatment bone marrow evaluations predominantly showed reduced myeloid maturation which normalised on G-CSF therapy in seven of 13 examined. Consistent clinical improvement, with reduced signs and symptoms of infections, was observed in response to prophylactic G-CSF ± prophylactic antibiotics. However, despite G-CSF and antibiotics, one adult patient died with multiple infections related to indwelling medical devices and gastrostomy site infection after 15.5 years on G-CSF and a paediatric patient required gastrostomy removal for recurrent abdominal wall cellulitis.

Peptidylarginine deiminase 4 (PAD4) is a key regulator of inflammation but its function in infections remains incompletely understood. We investigate PAD4 in the context of malaria and demonstrate a role in regulation of immune cell trafficking and chemokine production. PAD4 regulates liver immunopathology by promoting neutrophil trafficking in a Plasmodium chabaudi mouse malaria model. In human macrophages, PAD4 regulates expression of CXCL chemokines in response to stimulation with TLR ligands and P. falciparum. Using patient samples, we show that CXCL1 may be a biomarker for severe malaria. PAD4 inhibition promotes disease tolerance and may represent a therapeutic avenue in malaria.

Endobronchial fungal infection (EBFI) is notoriously difficult to diagnose early since it may present few systemic features and does not cause characteristic parenchymal lesions on lung CT scanning. We report a 9-year-old girl who suffered extended neutropenia following graft failure after haematopoietic stem cell transplantation (HSCT) for severe aplastic anaemia. CT scan prior to retransplantation was normal despite persistent cough but lobar collapse was shown on repeat scan 16 days later. The probable diagnosis of EBFI (later proven on bronchoscopy) was only suspected when subsequent chest X-ray (CXR) demonstrated lack of an air bronchogram in the partially collapsed lung. Early radiological suspicion resulted in multiagent antifungal therapy followed by delayed lobectomy, and led to this being the first reported case of Aspergillus EBFI not to result in respiratory failure.

Colorectal cancer (CRC) is a multi-stage process initiated through the formation of a benign adenoma, progressing to an invasive carcinoma and finally metastatic spread. Tumour cells must adapt their metabolism to support the energetic and biosynthetic demands associated with disease progression. As such, targeting cancer cell metabolism is a promising therapeutic avenue in CRC. However, to identify tractable nodes of metabolic vulnerability specific to CRC stage, we must understand how metabolism changes during CRC development. Here, we use a unique model system - comprising human early adenoma to late adenocarcinoma. We show that adenoma cells transition to elevated glycolysis at the early stages of tumour progression but maintain oxidative metabolism. Progressed adenocarcinoma cells rely more on glutamine-derived carbon to fuel the TCA cycle, whereas glycolysis and TCA cycle activity remain tightly coupled in early adenoma cells. Adenocarcinoma cells are more flexible with respect to fuel source, enabling them to proliferate in nutrient-poor environments. Despite this plasticity, we identify asparagine (ASN) synthesis as a node of metabolic vulnerability in late-stage adenocarcinoma cells. We show that loss of asparagine synthetase (ASNS) blocks their proliferation, whereas early adenoma cells are largely resistant to ASN deprivation. Mechanistically, we show that late-stage adenocarcinoma cells are dependent on ASNS to support mTORC1 signalling and maximal glycolytic and oxidative capacity. Resistance to ASNS loss in early adenoma cells is likely due to a feedback loop, absent in late-stage cells, allowing them to sense and regulate ASN levels and supplement ASN by autophagy. Together, our study defines metabolic changes during CRC development and highlight ASN synthesis as a targetable metabolic vulnerability in later stage disease.

Cytomegalovirus (CMV) infection is associated with increased transplant related mortality and decreased overall survival after stem cell transplantation (SCT) despite major advances in early detection, prophylaxis and treatment. This effect is most marked in CMV seropositive patients who have a statistically significant decrement in overall or disease free survival of 20–46% when compared to low risk (−/−) transplants (Boeckh Blood 2004 103: 2003–8). Transfer of cellular immunity from a seropositive donor results in reconstitution of T cells to CMV and protection from CMV disease post-SCT, and this underlies the recent development of cellular immunotherapeutic manoeuvres. As a centre looking to develop such therapy, we have carried out a retrospective analysis of a patient cohort in order to estimate how many patients would require this intervention. We used twice weekly quantitative PCR surveillance to analyse the CMV reactivation profiles of 104 recipients of 106 allogeneic SCT, transplanted between April 2002 and April 2004. Hence follow up was 5–27 months. The cohort comprised 41 adults and 65 children. Transplants were from related (42), unrelated (52) and haploidentical donors (12). T cell depletion was performed either (i) in vivo using either CAMPATH-1H (44 transplants) or ATG (5), (ii) ex vivo by either CD34 (8) or CAMPATH-1H in vitro (1), or (iii) by combinations of (i) and (ii) (26). SCTs were for malignancies in 92 cases and non-neoplastic disorders in 14. Many patients were considered high risk, necessitating short search to transplant times. A hierarchy of donor selection factors was considered: HLA matching was the primary determinant, with other factors including stem cell dose, age, gender and CMV status. Seventy-one patients were at risk of CMV reactivation. There were 28 episodes of CMV reactivation in 27 of these patients, with the following Recipient/Donor serostatus combinations: 0 (of 16) −/+, 22 (of 38) +/− and 6 (of 17) +/+. Seven patients (Group A) resolved their infections without intervention. Nine patients (Group B) resolved infections after antiviral drug treatment, whilst the remaining 12 reactivators (Group C) did not clear their CMV DNA load despite antiviral treatment (of whom 3 died, 1 relapsed and the remainder have ongoing CMV PCR positivity). As a minimum a CMV immunotherapy programme should allow prophylaxis or early treatment of all patients in groups B and C. However, using our current selection criteria only 5/21 cases had a CMV seropositive donor. Logistical problems e.g. CTL precursor frequency or availability of an immunodominant tetramer might have rendered some donors inappropriate providers of anti-CMV CTL. Thus a maximum of 5 out of 106 transplanted patients in our unit could have benefited, although this figure could be slightly improved by deliberate selection of CMV positive donors for CMV positive patients. Such numbers should be borne in mind by any centre contemplating the development of antiviral immunotherapy programmes.

Microsatellite analyses show that self-reported ethnicity often correlates poorly with true genetic ancestry. As unknown ancestral differences could potentially have an impact on transplant outcome, we developed an average allele length discrepancy (AALD) score to assess allele length discrepancy between donor/recipient (D/R) using microsatellites analysed routinely in post-transplant chimeric assessment. This was then compared with outcome in a homogeneously treated cohort of pediatric patients undergoing high-resolution sibling or matched unrelated donor transplantation for acute lymphoblastic leukemia (ALL). AALD scores formed a numeric continuum ranging from 0 to 1.4 (median 0.76) for sibling pairs and 0.8-2.17 (median 1.6) for high-resolution matched unrelated donor (HR-MUD) pairs. There was a trend for worse OS with increasing AALD score, which reached statistical significance above a threshold of 1.7 for OS. Patients whose transplants had an AALD score of ⩾ 1.8 had a risk of non-relapse mortality 4.9 times greater (P = 0.025) and relapse risk three times greater (P = 0.058) than those scoring o 1.8. This approach will now be explored in a Centre International for Blood and Marrow Transplantation Research (CIBMTR) study of 750 D/R pairs across all disease groups; if confirmed, it has the potential to improve donor selection for patients with multiple prospective donors.