Transplant-associated thrombotic microangiopathy (TA-TMA) is an under-recognized yet potentially devastating complication of hematopoietic stem cell transplantation which had increased awareness in recent years. This report summarizes territory-wide experience of paediatric TA-TMA in the Hong Kong Children’s Hospital from 1 April 2019 to 31 March 2021. Total six patients were identified among 73 transplants performed. Median duration of onset was 2.5 months post-HSCT. Three patients died while all 3 survivors suffered from stage 2 to 5 chronic kidney disease despite administration of eculizumab. To conclude, recognition and diagnosis of TA-TMA is challenging. Clinical utility of complement blockage with eculizumab is limited.

A 5-year-old girl had poor growth and unresolving pneumonia. There was persistent collapse-consolidation of the right middle lobe. CT thorax revealed bilateral bronchial wall thickening and dilatation. Bronchoscopy showed numerous endobronchial mucosal nodules, consisting of dense lymphoid infiltrates. Bacterial culture of the nodule biopsy suggested endobronchial actinomycosis. She had T-cell lymphopenia. Genetic test confirmed the diagnosis of activated phosphatidylinositol 3-kinase delta syndrome (APDS), an immunodeficiency condition.

Background Safety and immunogenicity of 3 doses of BNT162b2 and CoronaVac in adult and pediatric patients with inborn errors of immunity (IEIs) remain unknown. Intradermal vaccination may improve immunogenicity in immunocompromised patients. Our study (NCT04800133) aimed to determine the safety and immunogenicity in patients with IEIs receiving a 3-dose primary series of mRNA vaccine BNT162b2 (age 12+) or inactivated whole-virion vaccine CoronaVac (age 3+) in Hong Kong, including Omicron BA.1 neutralization, in a nonrandomized manner. Intradermal vaccination was also studied. Methods Thirty-nine patients were vaccinated, including 16 with homologous intramuscular 0.3ml BNT162b2 and 17 with homologous intramuscular 0.5ml CoronaVac. Two patients received 3 doses of intradermal 0.5ml CoronaVac, and 4 patients received 2 doses of intramuscular BNT162b2 and the third dose with intradermal BNT162b2. Adverse reactions and adverse events were tracked for 7 and 28 days after each dose. Antibody responses assessed included binding IgG antibody to wild-type (WT) spike receptor-binding domain (S-RBD IgG) and surrogate neutralization activity to WT and BA.1 viruses. T cell responses were examined by intracellular cytokine staining following stimulation with SARS-CoV-2 peptide pool(s). Results No safety concerns were identified. Inadequate antibody responses were found after 2 doses in patients with humoral immunodeficiencies and especially so against BA.1. Dose 3 of either vaccine increased S-RBD IgG response. T cell responses against SARS-CoV-2 antigens were detected in vaccinated IEI patients. Intradermal third dose vaccine led to high antibody response in 4 patients. Conclusions The primary vaccination series of BNT162b2 and CoronaVac in adults and children with IEIs should include 3 doses for optimal immunogenicity.

Background: Chronic benign neutropenia (CBN) and autoimmune neutropenia (AIN) are notoriously difficult to differentiate in children owing to their indistinguishable clinical course and varying availability and accuracy in the methods of anti-neutrophil antibody detection. This study aims to investigate whether the presence of anti-neutrophil antibody has implications on the disease course in Chinese children with AIN, as well as evaluating the various methods including LABScreen MULTI, granulocyte agglutination test (GAT) and granulocyte immunofluorescence test (GIFT) in anti-neutrophil antibody detection. Procedure: Chinese children under 18 years of age with neutropenia ≤ 1.5 x 109/L lasting 6 months or more in our single center were recruited into the study between 2016 to 2018. Patients with secondary causes of neutropenia were excluded. Blood for anti-neutrophil antibody and genotyping was taken once at the time of recruitment and subsequently when neutropenia recovered to ≥ 1.5 x 109/L. A combination of two in-house methods including GIFT, GAT and commercial kit LABScreenTM multipanel were used for the detection of antibodies. The age of onset, age of recovery, duration of neutropenia, gender, serial neutrophil counts, incidence of invasive infection, use of G-CSF were examined. Results: Using combined testing methods, anti-neutrophil antibody was detected in 30.8 % of patients and positivity was associated with more severe neutropenia, higher likelihood of infection and slower and later recovery compared to those without antibodies. Conclusions: The presence of anti-neutrophil antibody was useful in predicting the clinical course of patients with AIN. The use of combined testing methods increased the detection rate.