Primary hypogammaglobulinemia describes a heterogeneous group of immunoglobulin disorders mainly composed of X-linked agammaglobulinemia, common variable immunodeficiency, and selective immunoglobulin (Ig) A deficiency. The most serious problems are related to recurrent infections with high-grade encapsulated bacteria. However, a wide variety of rheumatologic disorders also occur in association with hypogammaglobulinemic states. Septic arthritis with usual bacterial pathogens such as Staphylococcus aureus, and unusual bacteria such as Mycoplasma and Ureaplasma species, have been described in these patients. An aseptic nonerosive polyarticular arthritis that resembles rheumatoid arthritis is seen in 10% to 30% of hypogammaglobulinemic patients. Autoimmune disorders such as immune thrombocytopenic purpura, immune hemolytic anemia, juvenile rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, Sjögren's syndrome, essential mixed cryoglobulinemia, chronic active hepatitis, and sarcoidosis have been reported in hypogammaglobulinemic patients. Finally, to complicate matters, many disease-modifying antirheumatic drugs, including gold, D-penicillamine, sulfasalazine, azathioprine, and cyclophosphamide, cause symptomatic hypogammaglobulinemia in some patients.