Transient hypogammaglobulinemia of infancy

Transient hypogammaglobulinemia of infancy (THI) is a primary immunodeficiency characterized by reduced levels of immunoglobulin G (IgG), sometimes accompanied by low immunoglobulin A (IgA) and/or immunoglobulin M (IgM), in infants and young children. It represents a prolongation and accentuation of the physiological nadir of immunoglobulin levels that normally occurs between 3 and 6 months of age, when maternal antibodies wane and the infant's own immune system has not yet fully matured. THI primarily affects the immune system, leaving affected children more susceptible to infections, particularly of the upper and lower respiratory tract (such as recurrent otitis media, sinusitis, and bronchitis), as well as gastrointestinal infections. Most children with THI present in the first year of life with recurrent mild to moderate infections. Some children may also experience allergic conditions such as eczema, food allergies, or wheezing. Importantly, THI is a self-limiting condition — immunoglobulin levels typically normalize by 2 to 4 years of age, though in some cases resolution may take longer, occasionally extending to age 5 or beyond. The diagnosis is made retrospectively once immunoglobulin levels have normalized and other primary immunodeficiencies have been excluded. Affected children generally have normal antibody responses to vaccines and normal T-cell function, which helps distinguish THI from more severe immunodeficiency disorders. Treatment is primarily supportive and depends on the severity and frequency of infections. Most children are managed with prompt and sometimes prophylactic antibiotic therapy for recurrent bacterial infections. Intravenous or subcutaneous immunoglobulin replacement therapy is reserved for the small subset of patients with severe, recurrent, or life-threatening infections who do not respond adequately to antibiotics alone. The prognosis for THI is excellent, as the vast majority of children outgrow the condition with full normalization of immunoglobulin levels and no long-term immune deficiency.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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