Transient hypogammaglobulinemia of infancy
Transient hypogammaglobulinemia of infancy is an exaggerated, prolonged dip in IgG that follows the decline of transplacental maternal antibody, usually apparent by 5 to 6 months of age with normal B cell numbers. Most infants need only observation and serial immunoglobulin monitoring; antibiotic prophylaxis or, rarely, immunoglobulin replacement is reserved for recurrent bacterial infection.
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What this article covers
- Overview
Definition: transient hypogammaglobulinemia of infancy is an exaggerated, prolonged version of the normal physiologic dip in serum immunoglobulin G (IgG) every infant passes through as maternal…
- Epidemiology
Typical patient: an otherwise healthy infant identified between 5 and 6 months of age, once transplacentally acquired IgG has fallen faster than endogenous synthesis has risen.
- Risk factors
Prematurity: birth before 37 weeks lowers transferred maternal IgG, since most placental transfer occurs in the third trimester, exaggerating and prolonging the nadir.
- Pathophysiology
Transplacental transfer: maternal IgG crosses the placenta via the neonatal Fc receptor, mostly in the third trimester, so a term newborn's serum IgG approximates or exceeds the mother's level at birth.
- Clinical features
Timing: a low immunoglobulin level or recurrent infection typically appears between 5 and 6 months of age, once transplacental IgG has waned, and can persist into the second year before resolving.
- Differential diagnosis
X-linked (Bruton) agammaglobulinemia: also apparent around 6 months of age as maternal IgG wanes, but peripheral B cells are absent or markedly reduced rather than normal, lymphoid tissue is scanty…
- Diagnosis
Diagnosis is established by: an age-inappropriately low serum IgG, with normal or only mildly low IgA and IgM, in an infant with a normal peripheral B cell count and intact vaccine-specific antibody…
- Management
First, reassure and observe: counsel that the condition is expected to resolve, continue routine immunization on schedule, including live-virus vaccines since T cell function is intact, and arrange primary-care follow-up.
- Complications
Recurrent otitis media: can cause conductive hearing loss and may prompt tympanostomy tube placement when episodes cluster within one season.
- Prognosis
Overall outcome: excellent; the large majority normalize IgG spontaneously by 2 to 5 years of age without long-term immune deficit.
- Prevention
No known primary prevention: the maturational delay is not preventable, so care focuses on monitoring and reducing infection burden.
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