Mold-sensitivity in children with moderate-severe asthma is associated with HLA-DR and HLA-DQ

Mediated Mendelian randomization analysis to determine the role of immune cells in regulating the effects of plasma metabolites on childhood asthma

Childhood asthma is a chronic inflammatory disease of the airways, the pathogenesis of which involves multiple factors including genetic predisposition, environmental exposure, and immune system regulation. To date, the causal relationships between immune cells, plasma metabolites, and childhood asthma remain undetermined. Therefore, we aim to utilize the Mendelian randomization approach to assess the causal relationships among immune cells, plasma metabolites, and childhood asthma. This study employed the Mendelian randomization approach to investigate how immune cells influenced the risk of childhood asthma by modulating the levels of plasma metabolites. Five Mendelian randomization methods-inverse variance weighted, weighted median, Mendelian randomization-Egger, simple mode, and weighted mode-were utilized to explore the causal relationships among 731 types of immune cells, 1400 plasma metabolites, and childhood asthma. The instrumental variables for the 731 immune cells and 1400 plasma metabolites were derived from a genome-wide association study meta-analysis. Additionally, sensitivity analyses were conducted to examine the robustness of the results, potential heterogeneity, and pleiotropy. The inverse variance weighted results indicated that HLA DR on dendritic cells (DC) is a risk factor for childhood asthma (OR: 1.08, 95% CI: 1.02-1.14). In contrast, HLA DR on DC acts as a protective factor against elevated catechol glucuronide levels (OR: 0.94, 95% CI: 0.91-0.98), while catechol glucuronide levels themselves serve as a protective factor for childhood asthma (OR: 0.73, 95% CI: 0.60-0.89). Thus, HLA DR on DC can exert a detrimental effect on childhood asthma through the negative regulation of catechol glucuronide levels. The mediating effect was 0.018, accounting for a mediation effect proportion of 23.4%. This study found that HLA DR on DC can exert a risk effect on childhood asthma through the negative regulation of catechol glucuronide levels, providing new strategies for the prevention and treatment of childhood asthma and guiding future research and clinical practice.

Aspergillus Sensitization and Allergic Bronchopulmonary Aspergillosis in Asthmatic Children: A Systematic Review and Meta-Analysis

Background: The prevalence of aspergillus sensitization (AS) and allergic bronchopulmonary aspergillosis (ABPA) in asthmatic children remains unclear. Objective: To systematically review the literature to estimate the prevalence of AS and ABPA in children with bronchial asthma. Methods: We searched the PubMed and Embase databases for studies reporting the prevalence of AS or ABPA in pediatric asthma. The primary outcome was to assess the prevalence of AS, while the secondary outcome was to evaluate the prevalence of ABPA. We pooled the prevalence estimates using a random effects model. We also calculated the heterogeneity and publication bias. Results: Of the 11,695 records retrieved, 16 studies with 2468 asthmatic children met the inclusion criteria. Most studies were published from tertiary centers. The pooled prevalence of AS in asthma (15 studies; 2361 subjects) was 16.1% (95% confidence intervals [CI], 9.3-24.3). The prevalence of AS was significantly higher in prospective studies, studies from India, and those from developing countries. The pooled prevalence of ABPA in asthma (5 studies; 505 children) was 9.9% (95% CI, 0.81-27.6). There was significant heterogeneity and publication bias for both outcomes. Conclusions: We found a high prevalence of AS and ABPA in asthmatic children. There is a need for community-based studies from different ethnicities using a standard methodology to ascertain the true prevalence of AS and ABPA in pediatric asthma.

[Association between HLA-class II genes and asthma susceptibility in a selected Constantine population]

Introduction

l’asthme est une maladie complexe causé par l’interaction de plusieurs gènes dont certains ont un effet protecteur et d’autres contribuent à l’apparition de la maladie. Cet article s’intéresse à une partie du bras court du chromosome 6 où siègent les gènes codant pour le complexe majeur d’histocompatibilité dénommé HLA qui joue un rôle important dans la pathogénèse de l’asthme.

Méthodes

notre étude inclut 61 personnes dont 30 personnes non asthmatiques non allergiques et 31 patients atteints d’asthme allergique depuis plus de 2 ans. Le statut atopique de l’asthme a été confirmé par les tests cutanés et le typage HLA classe II a été réalisé suivant le principe de la technique sérologique de séparation par Fluorobeads B.

Résultats

l’analyse statistique révèle que les gènes HLA-DR11 et DQ2 sont significativement plus fréquents chez les asthmatiques par rapport aux témoins, les résultats sont comme suit: le HLA-DR11 avec une p=0,05 et le HLA-DQ2 avec une p=0.002, cela nous a conduit à dire qu’il s’agit peut-être de marqueurs HLA en association avec l’asthme. En revanche le marqueur HLA-DQ6 était nettement plus important chez la population témoin que chez les sujets asthmatiques avec p=0.003.

Conclusion

cela nous a conduit à dire que les marqueurs HLA-DR11 et DQ2 pourraient être des gènes potentiels de susceptibilité à l’asthme, alors que HLA-DQ6 pourrait avoir un effet protecteur.

Can Controlling Endoplasmic Reticulum Dysfunction Treat Allergic Inflammation in Severe Asthma With Fungal Sensitization?

Severe asthma is a heterogeneous disease entity to which diverse cellular components and pathogenetic mechanisms contribute. Current asthma therapies, including new biologic agents, are mainly targeting T helper type 2 cell-dominant inflammation, so that they are often unsatisfactory in the treatment of severe asthma. Respiratory fungal exposure has long been regarded as a precipitating factor for severe asthma phenotype. Moreover, as seen in clinical definitions of allergic bronchopulmonary aspergillosis (ABPA) and severe asthma with fungal sensitization (SAFS), fungal allergy-associated severe asthma phenotype is increasingly thought to have distinct pathobiologic mechanisms requiring different therapeutic approaches other than conventional treatment. However, there are still many unanswered questions on the direct causality of fungal sensitization in inducing severe allergic inflammation in SAFS. Recently, growing evidence suggests that stress response from the largest organelle, endoplasmic reticulum (ER), is closely interconnected to diverse cellular immune/inflammatory platforms, thereby being implicated in severe allergic lung inflammation. Interestingly, a recent study on this issue has suggested that ER stress responses and several associated molecular platforms, including phosphoinositide 3-kinase-δ and mitochondria, may be crucial players in the development of severe allergic inflammation in the SAFS. Defining emerging roles of ER and associated cellular platforms in SAFS may offer promising therapeutic options in the near future.

Serum carotenoid and tocopherol concentrations and risk of asthma in childhood: a nested case-control study

BACKGROUND

The antioxidant hypothesis regarding the risk of asthma in childhood has resulted in inconsistent findings. Some data indicate that the role of antioxidants in childhood asthma risk may have a critical time window of effect, but only a well-designed longitudinal cohort study can clarify this hypothesis.

OBJECTIVE

To study the longitudinal associations between serum carotenoid and tocopherol concentrations during the first 4 years of life and asthma risk by the age of 5 years.

METHODS

Based on a case-control design nested within a Finnish birth cohort, 146 asthma cases were matched to 270 controls on birth time, sex, genetic risk, and birth place. Non-fasting blood samples were collected at the ages of 1, 1.5, 2, 3, and 4 years and serum carotenoids and tocopherols were analysed. Parents reported the presence and age at start of persistent doctor-diagnosed asthma in the child at the age of 5 years. Data analyses were conducted using generalized estimating equations.

RESULTS

We did not find strong associations between serum carotenoids and tocopherols and the risk of asthma based on age-specific and longitudinal analyses. Both lower and higher quarters of α-carotene and γ-tocopherol increased the risk of asthma.

CONCLUSIONS

The current findings do not support the suggestion that the increased prevalence of asthma may be a consequence of decreased intake of antioxidant nutrients. Moreover, we did not confirm any critical time window of impact of antioxidants on asthma risk. Replication of these findings in similar longitudinal settings will strengthen this evidence base.

Vitamin D intake during the first 4 years and onset of asthma by age 5: A nested case-control study

BACKGROUND

Early-life vitamin D intake has been linked to asthma risk in childhood, but the role of longitudinal vitamin D exposure has not been previously evaluated. We investigated the association between vitamin D intake during the first 4 years of life and asthma risk by age 5.

METHODS

Within a Finnish population-based birth cohort, 182 incident asthma cases were matched to 728 controls on sex, genetic risk for type 1 diabetes, delivery hospital, and time of birth. Vitamin D intake was assessed by age-specific 3 day food records. Parents completed a validated version of the International Study of Asthma and Allergies in Childhood questionnaire at 5 years.

RESULTS

At 3 months, supplements were the main source of vitamin D intake; intake from foods increased from 3 months on, mainly from fortified milk products. Vitamin D intake at each specific age was associated with an increased risk of any asthma, atopic, and non-atopic asthma, but only intake at 1 and 2 years was statistically significantly associated with asthma. Longitudinal vitamin D intake was associated with an increased risk of asthma (OR 1.24; 95%CI 1.00-1.53).

CONCLUSIONS

Increased vitamin D intake in childhood, particularly intake at 1 and 2 years of age, may increase risk of childhood asthma. This might reflect a true effect or residual confounding by lifestyle or environmental factors. Repeated assessment of vitamin D intake allowed evaluation of the longitudinal and age-dependent impact of vitamin D on the risk of asthma. Further longitudinal studies are required to confirm or question these findings.

Personalised medicine in asthma: from curative to preventive medicine

The concept of asthma has changed substantially in recent years. Asthma is now recognised as a heterogeneous entity that is complex to treat. The subdivision of asthma, provided by "cluster" analyses, has revealed various groups of asthma patients who share phenotypic features. These phenotypes underlie the need for personalised asthma therapy because, in contrast to the previous approach, treatment must be tailored to the individual patient. Determination of the patient's asthma phenotype is therefore essential but sometimes challenging, particularly in elderly patients with a multitude of comorbidities and a complex exposure history. This review first describes the various asthma phenotypes, some of which were defined empirically and others through cluster analysis, and then discusses personalisation of the patient's diagnosis and therapy, addressing in particular biological therapies and patient education. This personalised approach to curative medicine should make way in the coming years for personalised preventive and predictive medicine, focused on subjects at risk who are not yet ill, with the aim of preventing asthma before it occurs. The concept of personalised preventive medicine may seem a long way off, but is it really?

Clinical relevance of IgE-mediated sensitization against the mould Alternaria alternata in children with asthma

Background:

Asthma in childhood has a prevalence of 5–10% in Germany and severe asthma accounts for about 5% in this patient group. Positive predictive values for severe asthma are atopy, a positive family history and sensitizations against inhalative allergens. Alternaria is an important inhalative allergen and sensitization is suspected to correlate with severe and lethal asthma. We investigated the prevalence and impact of Alternaria sensitization in paediatric asthma.

Methods:

We reviewed paediatric patients with a diagnosis of low-grade, moderate and severe asthma. Data collection included concomitant atopic diseases, sensitization profiles, family history and prior hospitalization for asthma exacerbation.

Results:

A total of 207 paediatric patients (aged 1–17 years) were included in the study. Overall, 25% had low-grade asthma, 31% moderate and 44% severe asthma and 26% were formerly hospitalized. Alternaria sensitization was the most common in moulds, although without significant correlation with hospitalization and severe asthma. Alternaria sensitization increased with age and was significantly associated with co-sensitization against other moulds, grass pollen and cat epithelia. Allergic rhinitis was significantly correlated with hospitalization, independent of Alternaria sensitization.

Conclusions:

Alternaria sensitization was common and increased with age. No significant correlation was found between asthma degree, hospitalization rates and sensitization profiles. Alternaria sensitization demonstrated no isolated risk factor for severe asthma and hospitalization.

The spectrum of allergic fungal diseases of the upper and lower airways

Fungi cause a wide spectrum of fungal diseases of the upper and lower airways. There are three main phyla involved in allergic fungal disease: (1) Ascomycota (2) Basidiomycota (3) Zygomycota. Allergic fungal rhinosinusitis (AFRS) causes chronic rhinosinusitis symptoms and is caused predominantly by Aspergillus fumigatus in India and Bipolaris in the United States. The recommended treatment approach for AFRS is surgical intervention and systemic steroids. Allergic bronchopulmonary aspergillosis (APBA) is most commonly diagnosed in patients with asthma or cystic fibrosis. Long term systemic steroids are the mainstay treatment option for ABPA with the addition of an antifungal medication. Fungal sensitization or exposure increases a patient's risk of developing severe asthma and has been termed severe asthma associated with fungal sensitivity (SAFS). Investigating for triggers and causes of a patient's asthma should be sought to decrease worsening progression of the disease.

Anti-inflammatory actions of Chemoattractant Receptor-homologous molecule expressed on Th2 by the antagonist MK-7246 in a novel rat model of Alternaria alternata elicited pulmonary inflammation

Alternaria alternata is a fungal allergen linked to the development of severe asthma in humans. In view of the clinical relationship between A. alternata and asthma, we sought to investigate the allergic activity of this antigen after direct application to the lungs of Brown Norway rats. Here we demonstrate that a single intratracheal instillation of A. alternata induces dose and time dependent eosinophil influx, edema and Type 2 helper cell cytokine production in the lungs of BN rats. We established the temporal profile of eosinophilic infiltration and cytokine production, such as Interleukin-5 and Interleukin-13, following A. alternata challenge. These responses were comparable to Ovalbumin induced models of asthma and resulted in peak inflammatory responses 48h following a single challenge, eliminating the need for multiple sensitizations and challenges. The initial perivascular and peribronchiolar inflammation preceded alveolar inflammation, progressing to a more sub-acute inflammatory response with notable epithelial cell hypertrophy. To limit the effects of an A. alternata inflammatory response, MK-7246 was utilized as it is an antagonist for Chemoattractant Receptor-homologous molecule expressed in Th2 cells. In a dose-dependent manner, MK-7246 decreased eosinophil influx and Th2 cytokine production following the A. alternata challenge. Furthermore, therapeutic administration of corticosteroids resulted in a dose-dependent decrease in eosinophil influx and Th2 cytokine production. Reproducible asthma-related outcomes and amenability to pharmacological intervention by mechanisms relevant to asthma demonstrate that an A. alternata induced pulmonary inflammation in BN rats is a valuable preclinical pharmacodynamic in vivo model for evaluating the pharmacological inhibitors of allergic pulmonary inflammation.

HLA and asthma phenotypes/endotypes: a review

Asthma is a complex chronic inflammatory disease of the airways caused by the interaction of genetic susceptibility with environmental influences. Genome-wide association studies (GWAS) represent the most powerful approach for asthma, that have identified several genes (e.g., IL18R1, IL33, SMAD3, ORMDL3, HLA-DQ and IL2RB loci). HLA super-locus is a genomic region in the chromosomal position 6p21. Since no gene can be considered as an asthma gene, able to reflect the complex etiology and the heterogeneity of the disease the terms 'phenotype' and more recently 'endotype' have been used. This review, according to literature availability, focuses on the relationship between human leukocyte antigens (HLA) region specifically the HLA class II genes and different asthma phenotypes/endotypes, such as allergic asthma/Th2 associated, occupational and aspirin-sensitive asthma. The most common HLA haplotypes in the different asthma phenotypes are HLA-DRB1in allergic asthma, HLA-DQB1in occupational asthma and HLA-DPB1 in aspirin-sensitive asthma. However, it is difficult to study the role of class II genes in vivo because of the heterogeneity of human population, the complexity of MHC, and the strong linkage disequilibrium among different class II genes. Despite the variation and the inconsistency of the HLA haplotypes and alleles in different types of asthma, the association between HLA class II genes and asthma has been demonstrated in the majority of studies.

Food diversity in infancy and the risk of childhood asthma and allergies

BACKGROUND

Recently, the bacterial diversity of the intestinal flora and the diversity of various environmental factors during infancy have been linked to the development of allergies in childhood. Food is an important environmental exposure, but the role of food diversity in the development of asthma and allergies in childhood is poorly defined.

OBJECTIVE

We studied the associations between food diversity during the first year of life and the development of asthma and allergies by age 5 years.

METHODS

In a Finnish birth cohort we analyzed data on 3142 consecutively born children. We studied food diversity at 3, 4, 6, and 12 months of age. Asthma, wheeze, atopic eczema, and allergic rhinitis were measured by using the International Study of Asthma and Allergies in Childhood questionnaire at age 5 years.

RESULTS

By 3 and 4 months of age, food diversity was not associated with any of the allergic end points. By 6 months of age, less food diversity was associated with increased risk of allergic rhinitis but not with the other end points. By 12 months of age, less food diversity was associated with increased risk of any asthma, atopic asthma, wheeze, and allergic rhinitis.

CONCLUSION

Less food diversity during the first year of life might increase the risk of asthma and allergies in childhood. The mechanisms for this association are unclear, but increased dietary antigen exposure might contribute to this link.

Beneficial role of vitamin D3 in the prevention of certain respiratory diseases

There is evidence of aberrations in the vitamin D-endocrine system in subjects with respiratory diseases. Vitamin D deficiency is highly prevalent in patients with respiratory diseases, and patients who receive vitamin D have significantly larger improvements in inspiratory muscle strength and maximal oxygen uptake. Studies have provided an opportunity to determine which proteins link vitamin D to respiratory pathology, including the major histocompatibility complex class II molecules, vitamin D receptor, vitamin D-binding protein, chromosome P450, Toll-like receptors, poly(ADP-ribose) polymerase-1, and the reduced form of nicotinamide adenine dinucleotide phosphate. Vitamin D also exerts its effect on respiratory diseases through cell signaling mechanisms, including matrix metalloproteinases, mitogen-activated protein kinase pathways, the Wnt/β-catenin signaling pathway, prostaglandins, reactive oxygen species, and nitric oxide synthase. In conclusion, vitamin D plays a significant role in respiratory diseases. The best form of vitamin D for use in the treatment of respiratory diseases is calcitriol because it is the active metabolite of vitamin D3 and modulates inflammatory cytokine expression. Further investigation of calcitriol in respiratory diseases is needed.

Timing of infant feeding in relation to childhood asthma and allergic diseases

BACKGROUND

Emerging evidence questions current recommendations on the timing of infant feeding for the prevention of childhood allergies. The evidence for asthma is inconclusive.

OBJECTIVE

We sought to investigate the associations between the duration of breast-feeding and timing of introduction of complementary foods and the development of asthma and allergies by the age of 5 years.

METHODS

Data were analyzed for 3781 consecutively born children. The dietary exposures were categorized into thirds and analyzed as time-dependent variables. Asthma, allergic rhinitis, and atopic eczema end points were assessed by using the International Study of Asthma and Allergies in Childhood questionnaire, whereas IgE antibodies were analyzed from serum samples at the age of 5 years. Cox proportional hazard and logistic regressions were used for the analyses.

RESULTS

The median duration of exclusive and total breast-feeding was 1.4 months (interquartile range, 0.2-3.5 months) and 7.0 months (interquartile range, 4.0-11.0 months), respectively. Total breast-feeding of 9.5 months or less was associated with an increased risk of nonatopic asthma. Introduction of wheat, rye, oats, or barley at 5 to 5.5 months was inversely associated with asthma and allergic rhinitis, whereas introduction of other cereals at less than 4.5 months increased the risk of atopic eczema. Introduction of egg at 11 months or less was inversely associated with asthma, allergic rhinitis, and atopic sensitization, whereas introduction of fish at 9 months or less was inversely associated with allergic rhinitis and atopic sensitization.

CONCLUSION

Early introduction of wheat, rye, oats, and barley cereals; fish; and egg (respective to the timing of introduction of each food) seems to decrease the risk of asthma, allergic rhinitis, and atopic sensitization in childhood. Longer duration of total breast-feeding, rather than its exclusivity, was protective against the development of nonatopic but not atopic asthma, suggesting a potential differing effect of breast-feeding on different asthma phenotypes.

The role of vitamin D in asthma

Vitamin D metabolites are important immune-modulatory hormones and are able to suppress Th2-mediated allergic airway disease. Some genetic factors that may contribute to asthma are regulated by vitamin D, such as vitamin D receptor (VDR), human leukocyte antigen genes (HLA), human Toll-like receptors (TLR), matrix metalloproteinases (MMPs), a disintegrin and metalloprotein-33 (ADAM-33), and poly(ADP-ribosyl) polymerase- 1 (PARP-1). Vitamin D has also been implicated in asthma through its effects on the obesity, bacillus Calmettee Guérin (BCG) vaccination and high vitamin D level, vitamin D supplement, checkpoint protein kinase 1 (Chk1), plasminogen activator inhibitor-1 (PAI-1) and gamma delta T cells (gdT). Vitamin D plays a role in asthma and exerts its action through either genomic and/or non-genomic ways.

The effect of mold sensitization and humidity upon allergic asthma

INTRODUCTION

Humidity is commonly associated with increased airway hyperresponsiveness in asthma.

OBJECTIVE

To examine mold sensitization in patients with allergic asthma or allergic rhinitis and self-reports of humidity as exacerbating factors of clinical symptoms.

METHODS

A retrospective, cross-sectional study at a University hospital outpatient allergy and asthma clinic was performed. A total of 106 patients with either allergic asthma or allergic rhinitis completed standard prick-puncture skin testing with 17 allergens and controls and completed standardized forms addressing trigger factors for clinical symptoms.

RESULTS

Allergic asthmatics sensitized to Cladosporium were more likely to have a more severe asthma severity class (odds ratio = 4.26, confidence interval = 1.30-16.93). Sensitization to Alternaria, Cladosporium, Helminthosporium, Aspergillus and Dermatophagoides pteronyssinus in asthma was associated with higher likelihood for previous hospitalization, while sensitization to Cladosporium, Helminthosporium, Aspergillus, Dermatophagoides pteronyssinus and cockroach in asthma was associated with higher likelihood of having reduced pulmonary function based on forced expiratory volume in 1s. Furthermore, allergic asthmatics more commonly reported humidity as an exacerbating factor of symptoms than did patients only with allergic rhinitis (68.42% vs 42.86%, respectively; P < 0.05).

CONCLUSION

Mold sensitization is highly associated with more severe asthma, while humidity is more of an exacerbating factor in patients with allergic asthma as compared with allergic rhinitis alone. Further delineation between mold sensitization and humidity is needed to determine whether these are independent factors in asthma.

Fungi and allergic lower respiratory tract diseases

Asthma is a common disorder that in 2009 afflicted 8.2% of adults and children, 24.6 million persons, in the United States. In patients with moderate and severe persistent asthma, there is significantly increased morbidity, use of health care support, and health care costs. Epidemiologic studies in the United States and Europe have associated mold sensitivity, particularly to Alternaria alternata and Cladosporium herbarum, with the development, persistence, and severity of asthma. In addition, sensitivity to Aspergillus fumigatus has been associated with severe persistent asthma in adults. Allergic bronchopulmonary aspergillosis (ABPA) is caused by A fumigatus and is characterized by exacerbations of asthma, recurrent transient chest radiographic infiltrates, coughing up thick mucus plugs, peripheral and pulmonary eosinophilia, and increased total serum IgE and fungus-specific IgE levels, especially during exacerbation. The airways appear to be chronically or intermittently colonized by A fumigatus in patients with ABPA. ABPA is the most common form of allergic bronchopulmonary mycosis (ABPM); other fungi, including Candida, Penicillium, and Curvularia species, are implicated. The characteristics of ABPM include severe asthma, eosinophilia, markedly increased total IgE and specific IgE levels, bronchiectasis, and mold colonization of the airways. The term severe asthma associated with fungal sensitization (SAFS) has been coined to illustrate the high rate of fungal sensitivity in patients with persistent severe asthma and improvement with antifungal treatment. The immunopathology of ABPA, ABPM, and SAFS is incompletely understood. Genetic risks identified in patients with ABPA include HLA association and certain T(H)2-prominent and cystic fibrosis variants, but these have not been studied in patients with ABPM and SAFS. Oral corticosteroid and antifungal therapies appear to be partially successful in patients with ABPA. However, the role of antifungal and immunomodulating therapies in patients with ABPA, ABPM, and SAFS requires additional larger studies.

Severe asthma with fungal sensitization

A new phenotype of asthma has been described recently, namely severe asthma with fungal sensitization (SAFS). SAFS can be conceptualized as a continuum of fungal sensitization, with asthma at one end and allergic bronchopulmonary aspergillosis at the other. It is diagnosed by the presence of severe asthma, fungal sensitization, and exclusion of allergic bronchopulmonary aspergillosis. Because of the paucity of data and ambiguity in diagnostic criteria, SAFS is currently more of a diagnosis of exclusion than a specific entity. Treatment of SAFS initially should be similar to that of severe asthma, including the use of omalizumab. The potential role of itraconazole as a specific therapy in SAFS requires more evidence before it can be incorporated in routine practice. An urgent need exists for data regarding the prevalence, natural history, and clinical relevance of SAFS so that its exact characterization and importance as a specific subtype of asthma can be clearly defined. This review summarizes the current understanding of the pathogenesis, diagnosis, and management of SAFS.