Profiling B-cell Response: Hyperimmunoglobulin M Syndrome due to CD40 Deficiency

Hyperimmunoglobulin M (IgM) Type 3 (HIGM 3) syndromes are rare autosomal recessive disorders characterized by intrinsic B-cell defects that restricts immunoglobulin class usage. HIGM 3 due to the absence of CD40 on B-cells is incredibly rare and remains poorly characterized. We describe the B-cell profile of a 6-year-old patient with a previously uncharacterized homozygous mutation in TNFRSF5 (CD40).