Clinical characteristics and molecular analysis of 21 Chinese children with congenital agammaglobulinemia

Evaluation of respiratory complications in patients with X-linked and autosomal recessive agammaglobulinemia

BACKGROUND

Congenital agammaglobulinemia is the first primary immunodeficiency disorder characterized by a defect in B lymphocyte development and subsequently decreased immunoglobulin levels. These patients are prone to suffer from recurrent infections mostly involving the respiratory tract. In this study, we aimed to describe in detail respiratory tract complications as the most prominent clinical feature among agammaglobulinemic patients.

METHODS

A total number of 115 patients were included. Demographic, clinical, and genetic data were collected from the patients' medical records. Among the available patients, pulmonary function tests (PFTs) and/or high-resolution computed tomography (HRCT) were performed.

RESULTS

Respiratory tract complications (85.2%) especially pneumonia (62.6%) were the most prominent clinical features in our cohort. Among patients with abnormal PFT results (N = 19), a mixed respiratory pattern was observed in 36.8%. HRCT was carried out in 29 patients; Bhalla scoring-based evaluation of these patients indicated excellent (44.8%), followed by good (34.5%) and mild (20.7%) results. Bronchiectasis was found in 13 patients undergoing HRCT (44.8%). We found significant inverse correlations between the Bhalla score and incidence rate of pneumonia, as well as the presence of bronchiectasis. Patients with abnormal PFT results had statistically significant higher bronchiectasis frequency and lower Bhalla scores compared to those with normal results. Forty-one patients were deceased, and here, respiratory failure was the most common cause of death (45.5%).

CONCLUSION

High prevalence of respiratory tract infections among agammaglobulinemic patients and subsequent progression to permanent lung damage highlights the importance of implementing respiratory evaluation as part of routine follow-up program of agammaglobulinemic patients. Physicians should be aware of this and regularly monitor the respiratory function of these patients to allow for timely diagnosis and treatment initiation aiming to improve patients' prognosis and quality of life.

Clinical and genetic profiles of patients with X-linked agammaglobulinemia from southeast Turkey: Novel mutations in BTK gene

BACKGROUND

X-linked agammaglobulinemia (XLA) is characterized by absent or severely reduced B cells, low or undetectable immunoglobulin levels, and clinically by extracellular bacterial infections which mainly compromise the respiratory tract. We aimed to analyze the clinical, immunological and genetic characteristics of 22 male children with XLA.

METHODS

Twenty-two children with XLA from 12 unrelated families were enrolled in this study. Clinical and demographic features of patients, serum immunoglobulin levels, percentage of B cells and BTK gene mutations were reviewed retrospectively.

RESULTS

We identified 12 different mutations in 22 patients from 12 unrelated families. The most frequent type of mutation was premature stop codon (33.3%). Ten mutations had been reported previously including three missense mutations (c.1774T>C, c.1684C>T, c.83G>T), three premature stop codons (c.1558C>T, c.1573C>T, c.753G>A), two splice-site (c.683-1G>A, c.1567-12_1567-9delTTTG) and two small nucleotide deletions (c.902-904_delAAG, c.179_181delAGA). Two novel mutations of the BTK gene were also presented and included one splice-site mutation (c.391+1G>C) and one premature stop codon mutation (c.1243_1243delG). Six out of 12 mutations of the BTK gene were located in the SH1 domain, two in the PH domain, two in the SH3 domain and two in the SH2 domain. Three patients had a history of severe infection before diagnosis. We did not identify any correlation between severity of clinical symptoms and the genotype.

CONCLUSIONS

Our results show that mutations in southeast Turkey could be different from those in the rest of the world and molecular genetic tests are an important tool for early confirmed diagnosis of XLA.

Pediatric allergy and immunology in China

Over the past 30 years, China has enjoyed rapid economic development along with urbanization at a massive scale that the world has not experienced before. Such development has also been associated with a rapid rise in the prevalence of allergic disorders. Because of the large childhood population in the country, the burden of childhood allergic disorders has become one of the major challenges in the healthcare system. Among the Chinese centers participating in the International Study of Asthma and Allergies in Childhood, the data clearly showed a continuing rise in the prevalence of asthma, allergic rhinitis, and atopic eczema. However, the discipline of pediatric allergy in mainland China is still in its infancy due to the lack of formal training program and subspecialty certification. Clinicians and researchers are increasingly interested in providing better care for patients with allergies by establishing pediatric allergy centers in different regions of the country. Many of them have also participated in national or international collaborative projects hoping to answer the various research questions related to the discipline of pediatric allergy and immunology. It is our hope that the research findings from China will not only improve the quality of care of affected children within this country but also the millions of patients with allergies worldwide.

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.

Clinical and mutational features of Vietnamese children with X-linked agammaglobulinemia

BACKGROUND

X-linked agammaglobulinemia (XLA) is a primary immune deficiency characterized by recurrent bacterial infections and profoundly depressed serum immunoglobulin levels and circulating mature B cells. It is caused by mutations of the Bruton tyrosine kinase (BTK) gene and is the most common form of inherited antibody deficiency. To our knowledge, this is the first report of XLA from Vietnam.

METHODS

We investigated the BTK gene mutations and clinical features of four unrelated Vietnamese children.

RESULTS

The mean ages at onset and at diagnosis were 2.5 and 8 years, respectively. All patients had a medical history of otitis media, pneumonia, and septicemia at the time of diagnosis. Other infections reported included sinusitis, bronchiectasis, arthritis, skin infections, meningitis, and recurrent diarrhea. We identified one previously reported mutation (c.441G >A) and three novel mutations: two frameshifts (c.1770delG and c.1742 delG), and one nonsense (c.1249A >T).

CONCLUSIONS

The delayed diagnosis may be attributable to insufficient awareness of this rare disease on the background of frequent infections even in the immunocompetent pediatric population in Vietnam. Our results further support the importance of molecular genetic testing in diagnosis of XLA.

Distribution, clinical features and molecular analysis of primary immunodeficiency diseases in Chinese children: a single-center study from 2005 to 2011

METHODS

Two hundred three children with genetically proven primary immunodeficiency diseases (PIDs) from 197 unrelated families were enrolled from January 2005 to December 2011.

RESULTS

On the basis of criteria developed by the International Union of Immunological Societies, 79 patients were diagnosed as "other well-defined immunodeficiency syndromes" (38.9%), 62 (30.6%) with "predominant antibody deficiencies," 26 (12.8%) with "congenital defects of phagocyte," 25 (12.3%) with "T- and B-cell immunodeficiency" and 11 (5.4%) with "diseases of immune dysregulation." The median time to the diagnosis was 27.9 months and the patients had a wide range of clinical presentations. In addition, a total of 23 pathogenic genes were identified and 213 mutations were detected, including 42 novel mutations.

CONCLUSIONS

With the increase in the awareness of PIDs and diagnostic competence, more PID patients will be diagnosed and we will be able to more accurately identify the frequency and the distribution of PIDs in the most populous country in the world.

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

BACKGROUND

X-linked agammagobulinemia (XLA) is a primary immunodeficiency caused by Bruton's tyrosine kinase (BTK) gene mutation. XLA patients have an extremely small amount of peripheral B cells and profound deficiency in all immunoglobulin isotypes. We analyzed the clinical, immunologic, and molecular characteristics of children with XLA in an attempt to improve the diagnosis and treatment of XLA in China.

METHODS

Twenty children with XLA-compatible phenotypes from 18 unrelated families were enrolled in this study. The BTK gene was amplified and sequenced, followed by mutation analysis in these children and their female relatives.

RESULTS

Eighteen different mutations of the BTK gene were identified in the 20 patients. Eleven mutations had been reported previously including eight missense mutations (c.994C>T, c.1987C>A, c.1885G>T, c.502T>C, c.1085C>T, c.1816C>T, c.214C>T, c.1912G>A) and three nonsense mutations (c.1267T>A, c.1793C>G, c.1618C>T). Seven novel mutations of the BTK gene were also presented and included five missense mutations (c.134T>A, c.1646T>A, c.1829C>G, c.711G>T, c.1235G>A), one splice-site mutation (c.523+1G>A) and one insertion mutation (c.1024-1025in sTTGCTAAAGCAACTGCTAAAGCAAG). Eight out of 18 mutations of the BTK gene were located in the TK domain, 4 in the PH domain, 4 in the SH2 domain and 2 in the TH domain. Genetic study for carrier status was carried out in 18 families with definite BTK gene mutations. Nine carriers with BTK gene mutations were identified. Six families without carriers were detected, and 3 patients were not tested in this study.

CONCLUSION

Our results support that molecular genetic testing represents an important tool for early confirmed diagnosis of congenital agammaglobulinemia and may allow accurate carrier detection and prenatal diagnosis.

[Lymphocytopenia: aetiology and diagnosis, when to think about idiopathic CD4(+) lymphocytopenia?]

Une lymphopénie est définie par un nombre de lymphocytes circulants inférieur à 1500/mm³ chez l’adulte et 4500/mm³ chez l’enfant avant huit mois. La lymphopénie peut être globale ou sélective, affectant une population lymphocytaire particulière. Le diagnostic étiologique doit tenir compte de l’âge, du contexte, des manifestations clinicobiologiques associées et des thérapeutiques reçues. Les lymphopénies de l’adulte peuvent être liées schématiquement à : (1) une insuffisance de production (carence en zinc, corticothérapie, déficits immunitaires primitifs…), (2) un excès de catabolisme (radiothérapie, chimiothérapie, traitements immunosuppresseurs, infection par le VIH ou lupus systémique, etc.), (3) une modification de la répartition des lymphocytes (infections virales, choc septique, brûlures étendues, hypersplénisme, granulomatoses, etc.), (4) les étiologies multifactorielles ou non identifiées (insuffisance rénale chronique, certaines hémopathies lymphoïdes, tumeur solide, causes ethniques, etc.). Chez l’enfant, à ces étiologies s’ajoutent d’autres déficits immunitaires primitifs d’expression sévère (défaut des précurseurs thymiques, déficit cytokinique, défaut de synthèse des récepteurs des lymphocytes B et T et défaut de la transduction du signal ou des interactions cellulaires). La lymphopénie CD4⁺ idiopathique de l’adulte est un diagnostic d’élimination. Cette affection rare se définit par une lymphopénie T CD4⁺ inférieure ou égale à 300/mm³ ou inférieure ou égale à 20 % des lymphocytes totaux, persistante en l’absence de diagnostic alternatif. Elle peut être asymptomatique, s’associer à des infections à germes opportunistes, ou se compliquer de symptômes auto-immuns (en particulier cytopénies) ainsi que de néoplasies. Le traitement, calqué sur la prise en charge des patients infectés par le VIH, peut nécessiter le recours à une immunothérapie spécifique dont le bénéfice clinique reste à évaluer.