Selective IgA deficiency
Selective IgA deficiency is the most common primary antibody deficiency, defined by a serum IgA level below 7 mg/dL with normal IgG and IgM. Most patients are asymptomatic; management is supportive, treating sinopulmonary and gastrointestinal infections as they occur and using washed or IgA-deficient blood products to prevent anaphylactic transfusion reactions.
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What this article covers
- Overview
Selective IgA deficiency is the most common primary antibody deficiency, defined by an isolated fall in serum IgA to below 7 mg/dL with preserved IgG and IgM.
- Epidemiology
Prevalence: Selective IgA deficiency occurs in roughly 1 in 500 to 1 in 700 people of European ancestry, the most common primary immunodeficiency encountered in practice.
- Risk factors
Family history: A first-degree relative with selective IgA deficiency or CVID makes the same isolated defect more likely.
- Pathophysiology
Selective IgA deficiency arises from an arrest in the terminal differentiation of B cells into IgA-secreting plasma cells, while B-cell numbers, IgG, and IgM remain normal.
- Clinical features
Asymptomatic majority: Most patients have no unusual infection history and are found incidentally when immunoglobulins are checked for another reason.
- Differential diagnosis
Common variable immunodeficiency: Also causes recurrent sinopulmonary infection, but IgG is low, either IgA or IgM is low too, and vaccine responses are impaired, unlike the isolated IgA fall with normal IgG and IgM here.
- Diagnosis
Diagnostic criterion: The diagnosis is confirmed by serum IgA below 7 mg/dL (0.07 g/L) on at least two occasions after age 4, with normal IgG and IgM and no other cause of hypogammaglobulinemia.
- Management
First action: Treat sinopulmonary and gastrointestinal infections as they arise with standard antimicrobial therapy targeted to the organism; routine prophylactic antibiotics and routine…
- Complications
Recurrent sinopulmonary infection: Repeated bronchitis and pneumonia over years can lead to bronchiectasis if not promptly treated.
- Prognosis
Most patients have a normal life expectancy and never need directed treatment, since the majority stay asymptomatic for life.
- Prevention
Confirm before labeling: Because low IgA is often transient before age 4, avoid diagnosing selective IgA deficiency until a repeat measurement after age 4 confirms a persistently low level with normal IgG and IgM.
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Related articles
- Common variable immunodeficiency (CVID)
Common variable immunodeficiency is the most common symptomatic primary immunodeficiency, a defect in B-cell differentiation causing low immunoglobulins and recurrent sinopulmonary infections, usually diagnosed after puberty. Diagnosis rests on low IgG with low IgA or IgM plus impaired vaccine responses, and treatment is lifelong immunoglobulin replacement with prompt infection management.
- X-linked (Bruton) agammaglobulinemia
X-linked agammaglobulinemia is a BTK gene defect that arrests B-cell maturation, producing absent peripheral B cells and panhypogammaglobulinemia in boys with recurrent sinopulmonary infection after 6 months of age. Diagnosis rests on quantitative immunoglobulins, B-cell flow cytometry, and BTK sequencing; treatment is lifelong immunoglobulin replacement plus prompt antibiotics and avoidance of live vaccines.
- Celiac disease
Celiac disease is an immune-mediated small-intestinal enteropathy triggered by dietary gluten in genetically predisposed individuals, presenting with malabsorptive diarrhea, iron-deficiency anemia, or dermatitis herpetiformis. Diagnosis requires IgA tissue transglutaminase serology with a total IgA level while the patient still eats gluten, confirmed by duodenal biopsy showing villous atrophy, and the only treatment is a strict lifelong gluten-free diet.
- Giardiasis
Giardiasis is infection of the proximal small bowel with the protozoan Giardia lamblia (duodenalis), acquired from cysts in contaminated fresh water or food, causing malabsorptive, foul-smelling, greasy diarrhea with bloating and weight loss over weeks. Diagnosis rests on a stool antigen or nucleic acid test, and treatment is a short course of tinidazole, metronidazole, or nitazoxanide.
- Transfusion reactions
Transfusion reactions are a spectrum of immunologic and non-immunologic complications of blood product administration, ranging from a benign febrile reaction to fatal acute hemolysis, anaphylaxis, TRALI, or septic shock. The first step for any reaction is always to stop the transfusion; the type is then distinguished by timing, hemolysis markers, and hemodynamic and respiratory pattern, and each type has a specific treatment and prevention strategy.
- Anaphylaxis
Anaphylaxis is an acute, potentially fatal systemic hypersensitivity reaction from massive mast cell and basophil mediator release, presenting within minutes as skin, respiratory, cardiovascular, and gastrointestinal involvement after allergen exposure. It is a clinical, treat-first diagnosis, and intramuscular epinephrine is the immediate life-saving therapy.