Two thirds of patients have positive anti nuclear antibodies. The IgM levels are usually low and a low IgA is common. There is a poor antibody response to pneumococcal vaccines. The natural killer cells are low or low normal. Switched memory B cells (IgM, IgD, CD27+) may be present in the blood. Differential diagnosis Familial cold urticaria
PLAID syndrome
TEMPI syndrome
MASA syndrome
Bogart–Bacall syndrome
SAHA syndrome
IPEX syndrome
EAST syndrome
3C syndrome