Which organs are involved in Selective Immunoglobulin A (IgA) Deficiency (SIgAD)?

Organs Involved in Selective IgA Deficiency

Primary Organ Systems Affected

Selective IgA Deficiency primarily affects the respiratory tract and gastrointestinal tract, with secondary involvement of multiple organ systems through associated autoimmune and allergic manifestations. 1, 2

Respiratory System

The respiratory tract is the most commonly affected organ system in symptomatic SIgAD patients:

• Upper respiratory tract infections occur in approximately 17.5% of patients, manifesting as recurrent sinusitis and otitis media 3
• Lower respiratory tract involvement includes recurrent pneumonia in 6% of patients, with some developing bronchiectasis as a chronic complication 3
• Bronchiectasis develops in patients with concomitant immune defects (such as IgG subclass deficiency or defective specific antibody production), occurring in approximately 6% of cases with associated immunologic abnormalities 4, 3
• Ear involvement with recurrent otitis media affects 11.8% of patients, with 2% developing secondary deafness 3

Gastrointestinal System

The gastrointestinal tract is significantly affected due to the critical role of secretory IgA in mucosal immunity:

• Chronic diarrhea occurs in 6.5% of patients, often related to impaired mucosal defense and gut dysbiosis 3, 5
• Celiac disease is strongly associated with SIgAD, affecting 6.6% of patients—a much higher rate than the general population 3
• Giardia lamblia infections occur with increased frequency due to impaired mucosal immunity 6
• Gut dysbiosis with enriched proinflammatory bacterial phyla is present even in asymptomatic patients, only partially compensated by IgM and IgG 5

Endocrine System

Autoimmune endocrine disorders occur with increased frequency:

• Thyroid disease (thyroiditis) is the most common autoimmune manifestation in SIgAD patients 3, 7
• Type 1 diabetes mellitus shows increased association with IgA deficiency 6, 3

Hepatobiliary System

• Persistently elevated transaminases occur in some patients, suggesting hepatic involvement 3

Hematologic System

• Autoimmune cytopenias can develop as part of immune dysregulation 1, 3

Musculoskeletal System

• Juvenile chronic arthritis and other inflammatory arthropathies occur in the context of autoimmune complications 3

Skin

• Atopic dermatitis affects a significant proportion of patients with allergic manifestations 3
• Vitiligo has been documented as an autoimmune complication 3

Lymphoid Tissue

• Lymphadenopathy and splenomegaly are NOT characteristic features of SIgAD (unlike CVID), which helps distinguish these conditions 1
• Malignancies, particularly hematologic (lymphoma and leukemia), occur with increased frequency in 1.5% of pediatric patients 1, 3

Critical Clinical Pitfall

The majority of SIgAD patients (approximately 20-40%) remain asymptomatic throughout life, but symptomatic patients require long-term monitoring for complications across multiple organ systems 1, 3. Patients with isolated SIgAD have significantly lower rates of lower respiratory tract infections and bronchiectasis compared to those with associated immune defects (P=0.006 and P=0.015 respectively) 4.