Transient hypogammaglobulinemia of infancy

Transient hypogammaglobulinemia of infancy (THI) is a heterogeneous disorder characterized by a transient delay on reaching normal levels of IgG and IgA in the first 3 years of life. THI diagnosis can be defined only when a spontaneous resolution before age 4 occurs. THI is usually considered a variant of the normal, age-related development of the immune system. Clinical picture varies from asymptomatic cases to children presenting with recurrent respiratory and gastrointestinal infections, fever of unknown origin, and allergy. The pathophysiology includes delayed functional maturation of B cells, helper T cell defects or a defective T lymphocyte maturation which may affect B cell function. Defective memory B cells, low immunoglobulin levels, and delayed response to polysaccharides with failure to sustain protective antibody responses, were found to be predictors for primary immune deficiencies other than THI. Replacement treatment with immunoglobulin is not warranted unless the child suffers from persistent, recurrent, invasive infections.