Selective IgA Deficiency
Also written as: SIgAD — Selective IgA Deficiency
The most common primary antibody deficiency, defined by a serum IgA level below 0.07 g/L in individuals aged four years or older with normal IgG and IgM, often presenting with recurrent mucosal infections.
Full Definition
Selective IgA deficiency (SIgAD) is diagnosed when serum IgA is severely reduced (<0.07 g/L) in the presence of normal serum IgG and IgM concentrations and with other causes excluded. It affects approximately 1 in 300–500 individuals of European ancestry and has a highly variable clinical course: many individuals are asymptomatic, while others experience recurrent sinopulmonary infections, gastrointestinal disease, atopic conditions, or autoimmune disorders. An important clinical and editorial consideration is that patients with SIgAD may develop anti-IgA antibodies and are at risk for anaphylactic reactions to blood products or intravenous immunoglobulin containing IgA. Editors must correctly abbreviate this condition as 'selective IgA deficiency' or 'SIgAD', not 'IgA deficiency' alone, to distinguish it from secondary IgA reduction. Age thresholds for diagnosis must be accurately reported, as IgA levels are physiologically low in young children.
Usage
Usage note: Use 'selective' as a qualifier to distinguish from secondary IgA reduction. Always specify the diagnostic threshold (serum IgA <0.07 g/L) when first introduced in clinical documents. Flag anti-IgA antibody risk in clinical contexts.
In Context
- "Selective IgA deficiency was confirmed in the seven-year-old, who was subsequently counselled regarding the risk of transfusion-associated anaphylaxis." — Immunology clinic letter
- "The case report used 'IgA deficiency' without the qualifier 'selective'; the editor added the adjective to conform to diagnostic nomenclature." — Manuscript editing note