Features include always present findings: Decreased circulating IgE concentration, Everted upper lip vermilion, Partial absence of specific antibody response to tetanus vaccine, and Increased effector memory CD8+ T cell proportion and others; and common findings: Failure to thrive, Recurrent infections, Recurrent pneumonia, and B Acute Lymphoblastic Leukemia and others.

TCF3 function has not been fully characterized.

Agammaglobulinemia 8b, autosomal recessive is associated with mutations in the TCF3 gene on chromosome 19.

Genetic testing for TCF3 is available. Testing is considered confirmatory for diagnosis.

Phenotype severity distribution: 15 always present features, 8 common features.