About this Research Topic
Primary immunodeficiency diseases (PIDs), also known as inborn errors of the immune system (IEI), are a heterogeneous group of inherited disorders caused by genetic mutations that alter the immune system. They include more than 300 genetic defects that predispose patients to recurrent, prolonged, atypical and/or severe infections, autoimmunity, malignancy, auto-inflammation, immune dysregulation and allergic diseases. Although IEIs were previously believed to represent rare conditions, they are now known to affect 1 of every 1,200 to 2,000 individuals, with growing prevalence due to increased recognition because the threshold to perform exome sequencing is constantly lowered.
Recent evidence suggests that frequent allergic manifestations include eczema, allergic rhinitis, asthma, and food allergy may represent the expression of an underlying immunodeficiency and/or immune dysregulation. Furthermore, it is now clear that in some IEI, allergic symptoms may dominate the clinical presentation. In particular, the allergic triad defined by increased IgE, eosinophilia, and eczema is shared by different IEI that may be misdiagnosed as common allergic diseases. The diagnosis of IEI in the context of an allergic phenotype is crucial to ensure prompt diagnosis and appropriate treatment.
The pathogenesis of atopic manifestations are multifactorial, with a dysregulation of the immune system with an increased Th2 signaling and elevated levels of Th2-cytokines, such as interleukin-4 (IL-4), IL-5, IL-13, and IL-31.
Eosinophilia in association with IEIs is well known and classically include Wiskott Aldrich syndrome (WAS), hyper IgE syndromes (HIES), Omenn syndrome (OS), immunodysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome, atypical complete DiGeorge syndrome, Netherton’s syndrome and severe dermatitis—multiple allergies and metabolic wasting (SAM) syndrome. Moreover, ZAP70 deficiency, autoimmune lymphoproliferative syndrome (ALPS), selective IgA deficiency, and adenosine deaminase (ADA) deficiency have also appeared in the differential diagnosis of eosinophilia and elevated IgE.
Although IEIs are rare, it is important to distinguish them from atopic manifestations associated with eosinophilia and elevated IgE (such as AD), because their prognosis and treatment are completely different and an early diagnosis of IEIs is essential to prevent complications and irreversible damage.
The red flags that help us to differentiate between these diseases may include eczematous skin lesion manifesting prior to two months of life, disseminated or recurrent viral, bacterial, or fungal infections, mucocutaneous candidiasis, purpura, failure to thrive, chronic diarrhea, abnormalities of connective tissue or a history of familial consanguinity. A differential blood count, as well as a lymphocyte subset analysis, total immunoglobulin levels, and vaccination titers can help the clinician to decide whether a patient with eczematous skin lesions and elevated serum IgE should be referred to a clinical immunologist for a full immunological work-up and broad genetic analysis.
In this Research Topic, we welcome the submission of Original Research and Review articles covering, but not limited to, the following subtopics:
1. Specific inborn errors of the immune system including:
• Wiskott Aldrich syndrome
• Hyper IgE syndromes: AD - STAT3, gp130, ZNF341, IL6R; AR - DOCK8, ARPC1b, CARD11
• Omenn syndrome
• Immunodysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome
• Atypical complete DiGeorge syndrome
• Netherton’s syndrome
• Severe dermatitis—multiple allergies and metabolic wasting (SAM) syndrome
2. Inborn errors of immunity with atopic phenotypes: A practical guide for allergists
3. Eosinophilia associated with Inborn errors of immunity syndromes
Keywords: Inborn errors of the immune system, Atopy, Eosinophils, Elevated IgE
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