Clinical features and mutation analysis of X-linked agammaglobulinemia in 20 Chinese patients

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.

Ecthyma gangrenosum due to Pseudomonas aeruginosa sepsis as initial manifestation of X-linked agammaglobulinemia: a case report

BACKGROUND

X-linked agammaglobulinemia (XLA, OMIM#300,300), caused by mutations in the Bruton tyrosine kinase (BTK) gene, is a rare monogenic inheritable immunodeficiency disorder. Ecthyma gangrenosum is a cutaneous lesion caused by Pseudomonas aeruginosa that typically occurs in patients with XLA and other immunodeficiencies.

CASE PRESENTATION

We report the case of a 20-month-old boy who presented with fever, vomiting, diarrhea, and ecthyma gangrenosum. Blood, stool, and skin lesion culture samples were positive for P. aeruginosa. A diagnosis of XLA was established, and the c.262G > T mutation in exon 4 of BTK was identified with Sanger sequencing. Symptoms improved following treatment with antibiotics and immunoglobulin infusion.

CONCLUSIONS

Primary immunodeficiency (i.e., XLA) should be suspected in male infants with P. aeruginosa sepsis, highlighting the importance of genetic and immune testing in these patients.

Targeted next-generation sequencing for genetic diagnosis of 160 patients with primary immunodeficiency in south China

BACKGROUND

Primary immunodeficiency disorders (PID) is a group of heterogeneous diseases mainly characterized by severe and recurrent infections and an increased susceptibility to lymphoproliferative, atopic, and autoimmune conditions. The clinical diagnosis should preferably be complemented by a genetic diagnosis. To date, PID-related reports from China seldom attempt to make a genetic test for their patients.

METHODS

Our study aimed to evaluate demographic data, clinical manifestations, and molecular diagnosis of PID patients from southern China. Moreover, by comparison with previous reports, we provide a picture of the current status of PID in mainland China. A total number of 160 pediatric PID patients (106 males and 54 females) were enrolled, and targeted next-generation sequencing was conducted using 269 PID-related genes and subsequently confirmed by Sanger sequencing and familial segregation analysis.

RESULT

The autoinflammatory disease group was the most common subcategory of PID (20%), followed by immune dysregulation (17.5%) and combined immunodeficiencies (16.2%). Antibody deficiency disorders were identified in only 11.9% of the cohort. The putative causative gene was identified in 70 patients (43.8%), and an X-linked pattern was found in 45.7% of the genetically diagnosed patients.

CONCLUSION

The current study provides the first collective study of PID phenotypes and genotypes in south China and provides a strong argument for the diagnostic application of targeted next-generation sequencing panels in patients with suspected PID.

Prevalence of BTK mutations in male Algerian patterns with agammaglobulinemia and severe B cell lymphopenia

X linked agammaglobulinemia (XLA) is the first described primary immunodeficiency and the most common form of agammaglobulinemia. It is characterized by susceptibility to recurrent infections, profound decrease of all immunoglobulin isotypes and very low level of B lymphocytes in peripheral blood. The disorder is caused by mutations in the Bruton's Tyrosine Kinase (BTK). Nine male patients suspected to have XLA from nine unrelated families were enrolled in this study. We performed sequencing of the BTK gene in all nine patients, and in the patients' relatives when possible. The XLA diagnosis was confirmed for six patients with six different mutations; we identified a novel mutation (c.1522G>A) and five known mutations. One third of nine unrelated patients do not have mutations in BTK and thus likely suffer from autosomal recessive agammaglobulinemia in the setting of consanguinity. Our results support that the autosomal recessive agammaglobulinemia can be more common in Algeria.

Splice-correction strategies for treatment of X-linked agammaglobulinemia

X-linked agammaglobulinemia (XLA) is a primary immunodeficiency disease caused by mutations in the gene coding for Bruton’s tyrosine kinase (BTK). Deficiency of BTK leads to a developmental block in B cell differentiation; hence, the patients essentially lack antibody-producing plasma cells and are susceptible to various infections. A substantial portion of the mutations in BTK results in splicing defects, consequently preventing the formation of protein-coding mRNA. Antisense oligonucleotides (ASOs) are therapeutic compounds that have the ability to modulate pre-mRNA splicing and alter gene expression. The potential of ASOs has been exploited for a few severe diseases, both in pre-clinical and clinical studies. Recently, advances have also been made in using ASOs as a personalized therapy for XLA. Splice-correction of BTK has been shown to be feasible for different mutations in vitro, and a recent proof-of-concept study demonstrated the feasibility of correcting splicing and restoring BTK both ex vivo and in vivo in a humanized bacterial artificial chromosome (BAC)-transgenic mouse model. This review summarizes the advances in splice correction, as a personalized medicine for XLA, and outlines the promises and challenges of using this technology as a curative long-term treatment option.

[X-linked agammaglobulinemia: experience in a Portuguese hospital]

INTRODUCTION

X-Linked agammaglobulinemia (XLA) is characterized by an arrest of B cell differentiation, leading to recurrent bacterial infections. Lifelong immunoglobulin replacement therapy (IRT) is indicated to prevent infections and their complications.

MATERIAL AND METHODS

A retrospective study of patients with XLA followed in a level three hospital was performed; data was collected retrospectively by review of clinical files.

RESULTS

XLA was diagnosed in 9 children. One (11%) had a positive family history with a prenatal diagnosis. Infection was the clinical presentation in all the others (89%), at an average age of 13 months; diagnosis was established at a mean age of 3.4 years. Acute otitis media (7/9) and pneumonia (5/9) were the most frequently observed. Seven (78%) presented serum immunoglobulin G (IgG) levels below 200mg/dL and all of them had CD19(+) B cells below 2%. Neutropenia was present at diagnosis in three patients (33%). Bruton tyrosine kinase (BTK) mutations were identified in all cases. Intravenous IRT was initiated, switched later to subcutaneous administration, in all. The mean time of follow-up was 10.7 years with cumulative time of 97 years. Eight children (89%) achieved IgG serum levels above 800 mg/dL. One presented lower values due to renal loss. No deaths occurred. After diagnosis the most frequent infections were acute otitis media (6/9). In spite of stable adequate IgG levels on IRT, two patients developed bronchiectasis.

CONCLUSIONS

XLA overall prognosis is good, as long as patients have an early and adequate treatment. However, bronchiectasis can occur even on adequate immunoglobulin replacement therapy.

Clinical targeting of mutated and wild-type protein tyrosine kinases in cancer

Clinical therapies for cancer have evolved from toxic, nontargeted agents to manageable, highly targeted therapies. Protein tyrosine kinases are a family of signaling molecules implicated in nearly every cancer type and are the foundation for the development of modern targeted agents. Recent genomic analyses have identified activating mutations, translocations, and amplifications of tyrosine kinases. Selective targeting of these genetically altered tyrosine kinases has resulted in significant clinical advances, including increased patient survival. This indicates that altered protein tyrosine kinases are the main drivers of many different cancers. However, lost during analyses of genetic lesions are the contributions of activated, wild-type kinases on tumor-dependent pathways. New approaches in phosphoproteomic technologies have identified several wild-type tyrosine kinase activation states, suggesting that non-genetically altered kinases can be essential "nodes" for signal transduction. Here, we summarize the evidence supporting the common mechanisms of protein tyrosine kinase activation in cancer and provide a personal perspective on the kinases BCR-ABL and BTK, as well as nonmutated kinase targets in prostate cancer, through our work. We outline the mechanisms of tyrosine kinase activation in the absence of direct mutation and discuss whether non-genetically altered tyrosine kinases or their associated downstream signaling pathways can be effectively targeted.