Haploidentical Hematopoietic Stem Cell Transplantation for XIAP Deficiency: a Single-Center Report

Inborn errors of immunity in mainland China: the past, present and future

Inborn errors of immunity (IEI), also known as primary immunodeficiency diseases, comprise a group of rare genetic disorders that affect the development or/and function of the immune system. These disorders predispose individuals to recurrent infections, autoimmunity, cancer and immune dysregulations. The field of IEI diagnosis and treatment in mainland China has made significant strides in recent years due to advances in genome sequencing, genetics, immunology and treatment strategies. However, the accessibility and affordability of diagnostic facilities and precision treatments remain variable among different regions. With the increasing government emphasis on rare disease prevention, diagnosis, and treatment, the field of IEI is expected to progress further in mainland China. Herein, we reviewed the development and current state of IEI in mainland China, highlighting the achievements made, as well as opportunities and challenges that lie ahead.

Phenotype, genotype, treatment, and survival outcomes in patients with X-linked inhibitor of apoptosis deficiency

BACKGROUND

X-linked inhibitor of apoptosis (XIAP) deficiency is a rare, primary immunodeficiency disease caused by XIAP gene mutations. A broad range of phenotype, severity, and age of onset present challenges for patient management.

OBJECTIVE

To characterize the phenotype, treatment, and survival outcomes of XIAP deficiency and assess parameters influencing prognosis.

METHODS

Data published from 2006-2020 were retrospectively analyzed.

RESULTS

167 patients from 117 families with XIAP deficiency were reported with 90 different mutations. A wide spectrum of clinical features were seen, of which hemophagocytic lymphohistiocytosis (HLH) and inflammatory bowel disease (IBD) were the most common. Patients frequently developed multiple features with no clear genotype-phenotype correlation. 117 patients were managed conservatively and 50 underwent hematopoietic stem cell transplantation (HSCT), with respective overall survival probabilities of 90% and 53% at age 16 years. The predominant indication for HSCT was early-onset HLH. Active HLH and myeloablative conditioning regimens increased HSCT-related mortality, although HSCT outcome was much better after 2015 than before. For conservatively managed patients reaching adulthood, survival probabilities were 86% at age 30 years and 37% by age 52 years, with worse outcomes for patients developing the disease before the age of 5 years or with new disease features in adulthood. 9 asymptomatic mutation carriers were identified with a median age of 13.5 years.

CONCLUSIONS

Our study demonstrates the variable nature of XIAP deficiency which evolves over life for individual patients. Better therapeutic strategies and prospective studies are required to reduce morbidity and mortality and improve decision-making and long-term outcomes for patients with XIAP deficiency.

Haploidentical hematopoietic stem cell transplantation for pediatric patients with chronic active Epstein-Barr virus infection: a retrospective analysis of a single center

BACKGROUND

This study aimed to evaluate the feasibility and clinical effect of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for the treatment of pediatric patients with chronic active Epstein-Barr virus infection (CAEBV).

METHODS

Children with CAEBV who did not have matched donors and underwent haplo-HSCT in Beijing Children's Hospital, Capital Medical University, from October 2016 to June 2020 were analyzed retrospectively. Data relating to the clinical manifestations, engraftment, and prognosis of the children were extracted from medical records.

RESULTS

Twenty-five patients, including 16 males and 9 females, with an onset age of 5.0 ± 2.6 years and a transplantation age of 6.9 ± 2.9 years, were enrolled in this study. The mean time from diagnosis to transplantation was 3.8 (2.0-40.2) months. The mean observation time was 19.0 ± 12.0 months. Three patients received the reduced intensity conditioning regimen, and the remaining patients all received the modified myeloablative conditioning regimen. By the end of the follow-up, 23 patients were characterized by disease-free survival (DFS), 22 were characterized by event-free survival (EFS), and two died. One of the patients died of thrombotic microangiopathy (TMA), and another died of graft versus host disease (GVHD); this patient discontinued the treatment for economic reasons. The 3-year overall survival (OS) rate was estimated to be 92.0% ± 5.4%, and the 3-year EFS rate was estimated to be 87.4% ± 6.8%. All active patients survived after HSCT event-free. Acute GVHD degrees 1-3 were observed in ten patients (40.0%), and degree IV was observed in six (24.0%), who were all cured except for one patient. Chronic GVHD was observed in nine (36.0%), and most of these cases were mild. The incidence of TMA and veno-occlusive disease (VOD) was 28.0% and 4.0%.

CONCLUSIONS

Haploidentical hematopoietic stem cell transplantation is safe and effective in the treatment of pediatric CAEBV and can be used as an alternative therapy without matched donors or emergency transplantation. Patients with active disease before HSCT also benefited from haplo-HSCT. Haplo-HSCT requires careful monitoring for complications, such as GVHD and TMA. Early detection of TMA and timely treatment can reduce mortality and can improve the survival rate.

Evolution of Our Understanding of XIAP Deficiency

X-linked inhibitor of apoptosis (XIAP) deficiency is a rare inborn error of immunity first described in 2006. XIAP deficiency is characterised by immune dysregulation and a broad spectrum of clinical manifestations, including haemophagocytic lymphohistiocytosis (HLH), inflammatory bowel disease (IBD), hypogammaglobulinemia, susceptibility to infections, splenomegaly, cytopaenias, and other less common autoinflammatory phenomena. Since the first description of the disease, many XIAP deficient patients have been identified and our understanding of the disease has grown. Over 90 disease causing mutations have been described and more inflammatory disease manifestations, such as hepatitis, arthritis, and uveitis, are now well-recognised. Recently, following the introduction of reduced intensity conditioning (RIC), outcomes of allogeneic haematopoietic stem cell transplantation (HSCT), the only curative treatment option for XIAP deficiency, have improved. The pathophysiology of XIAP deficiency is not fully understood, however it is known that XIAP plays a role in both the innate and adaptive immune response and in immune regulation, most notably through modulation of tumour necrosis factor (TNF)-receptor signalling and regulation of NLRP3 inflammasome activity. In this review we will provide an up to date overview of both the clinical aspects and pathophysiology of XIAP deficiency.