Factors Affecting Immunoglobulin Levels

Primary Immunodeficiency Disorders

Agammaglobulinemia causes very low or undetectable immunoglobulins with absent or severely reduced B cells, typically presenting in the first 2 years of life with recurrent bacterial respiratory infections 1
Common Variable Immunodeficiency (CVID) produces variable reduction in ≥2 immunoglobulin classes with normal or moderately reduced B-cell numbers, often diagnosed after age 4 years 1
Selective IgA Deficiency is defined by IgA <7 mg/dL with normal IgG and IgM levels in patients older than 4 years, affecting approximately 1 in 300-700 white individuals 1
IgG subclass deficiencies can occur with normal total IgG levels but deficiency in one or more subclasses (IgG1-4), though approximately 2.5% of the population will automatically be "deficient" in at least one subclass by statistical definition 1

Antiepileptic drugs (phenytoin, carbamazepine, valproic acid, zonisamide) can cause reversible selective IgA deficiency and hypogammaglobulinemia 2

Nephrotic syndrome causes hypogammaglobulinemia due to urinary protein loss, diagnosed by 24-hour urine protein, urine protein/creatinine ratio, and urinalysis 2
Protein-losing enteropathy results in gastrointestinal protein loss with chronic diarrhea, assessed by stool alpha-1 antitrypsin clearance and intestinal imaging 2
Lymphatic disorders disrupt lymphatic drainage leading to protein loss 2
A critical distinguishing feature is that albumin and total protein levels will also be low in protein loss syndromes, unlike true immunodeficiency where only immunoglobulins are affected 2

Waldenström macroglobulinemia causes monoclonal IgM elevation, with treatment indicated when IgM levels exceed 60 g/L due to imminent risk of symptomatic hyperviscosity 3
Systemic lupus erythematosus (SLE) patients show variable immunoglobulin changes after pneumococcal vaccination, with some studies showing IgG and IgA levels decreasing by day 28 post-vaccination, though remaining in normal range 4
Good syndrome (thymoma-associated immunodeficiency) presents with late-onset combined immunodeficiency phenotype similar to CVID but with thymoma present 2
High erythrocyte sedimentation rate (ESR), high SLEDAI scores, and active disease correlate with poor immunological responses to vaccination in SLE patients 4

IgG4 is present in very low concentrations in children younger than 10 years, and therefore IgG4 deficiencies should not be diagnosed before age 10 years 1
Older age correlates with poorer post-immunization antibody titers (r=0.30, p=0.02) 4
Earlier disease onset in SLE correlates with poorer immunological response (r=0.43, p=0.02) 4

Prior to administering intravenous immunoglobulin (IVIG), serum immunoglobulin levels must be measured because patients with selective IgA deficiency may develop anaphylactic reactions, and pre-existing hypergammaglobulinemia may become aggravated leading to hyperviscosity 5, 6
Rituximab can cause a transient increase in serum IgM in 30-80% of patients, which may exacerbate hyperviscosity symptoms but doesn't indicate treatment failure 3
Prednisolone dosage is statistically associated with low antibody response to pneumococcal vaccination 4