Table 1. Characteristics of adults with IgGSD with and without subnormal IgG2 (<117 mg/dL)a.
| Characteristic | Subnormal IgG2 (n = 18) | No subnormal IgG2 (n = 218) | Value of p |
|---|---|---|---|
| Women, % (n) | 94.4 (17) | 79.4 (173) | 0.2110 |
| Mean age, y (± 1 SD) | 52 ± 11 | 50 ± 13 | 0.4455 |
| Upper respiratory tract infection, % (n) | 94.4 (17) | 93.6 (204) | ~1.0000 |
| Lower respiratory tract infection, % (n) | 77.8 (14) | 81.7 (178) | 0.7522 |
| Upper and lower respiratory tract infection, % (n) | 72.2 (13) | 77.1 (168) | 0.5761 |
| Autoimmune condition(s), % (n) | 44.4 (8)b | 47.2 (103)c | ~1.0000 |
| Atopy, % (n) | 44.4 (8)d | 28.0 (61)e | 0.1767 |
| Other allergy, % (n) | 61.1 (11) | 45.2 (99) | 0.2260 |
| Frequent/severe respiratory tract infection in first-degree relatives, % (n) | 22.2 (4) | 40.8 (89) | 0.1391 |
| Subnormal IgG (<700 mg/dL), % (n) | 66.7 (12) | 37.2 (81) | 0.0218 |
| Subnormal IgG1 (<422 mg/dL), % (n) | 50.0 (9) | 68.3 (149) | 0.1235 |
| Median IgG2, mg/dL (range) | 105 (83, 116) | 257 (117, 644) | <0.0001 |
| Subnormal IgG3 (<41 mg/dL), % (n) | 94.4 (17) | 67.4 (147) | 0.0155 |
| Subnormal IgG4 (<1 mg/dL), % (n) | 5.6 (1) | 5.0 (11) | ~1.0000 |
| Subnormal IgA (<70 mg/dL) | 33.3 (6)f | 4.1 (9)g | 0.0003 |
| Subnormal IgM (<40 mg/dL) | 0 | 23.4 (51) | 0.0156 |
a Abbreviations: IgGSD, immunoglobulin G subclass deficiency; IgG1, immunoglobulin G1; IgG2, immunoglobulin G2; IgG3, immunoglobulin G3; IgG4, immunoglobulin G4; SD, standard deviation. No patient had monoclonal gammopathy detected by serum electrophoresis and immunofixation.
b Eight patients (44.4%) had an autoimmune condition(s): rheumatoid arthritis (4); autoimmune/Hashimoto thyroiditis (3); lupus (2); Sjögren syndrome (2); anticardiolipin antibody syndrome (1); and positive anti-nuclear antibody ≥1:80 without greater specificity (1). Three patients (16.7%) had two or more autoimmune conditions.
c One hundred and three patients (47.2%) had an autoimmune condition(s): autoimmune/Hashimoto thyroiditis (39); rheumatoid arthritis (20); Sjögren syndrome (20); systemic lupus erythematosus (20); inflammatory arthritis not otherwise specified (6); psoriatic arthritis (6); ankylosing spondylitis (5); Graves disease (4); psoriasis (4); Raynaud phenomenon (4); Crohn disease (3); pernicious anemia (3); positive anti-nuclear antibody ≥1:80 without greater specificity (3); undifferentiated connective tissue disorder (3); autoimmune diabetes (2); Behçet disease (2); multiple sclerosis (2); ulcerative colitis (2); anti-cardiolipin antibody syndrome (1); autoimmune hemolytic anemia (1); autoimmune uveitis (1); glutamic acid decarboxylase autoantibody (1); Guillain-Barré syndrome (1); myasthenia gravis (1); and polymyalgia rheumatica (1). Forty-two patients (19.3%) had two or more autoimmune conditions.
d Seven patients had allergic asthma. One other patient had allergic rhinitis.
e Sixty-one patients had atopy (52 allergic asthma; 15 allergic rhinitis; 3 allergic dermatitis). Each of eight patients had two (or three) subtypes of atopy.
f The lowest IgA level observed in this subgroup was 32 mg/dL. Four of these 18 patients had both subnormal IgG and subnormal IgA.
g The lowest IgA level observed in this subgroup was 3 mg/dL. None of these 218 patients had both subnormal IgG and subnormal IgA.