selective IgM deficiency (MONDO_0018039) (SIgMD) is a rare immune disorder that has been reported in association with serious infections, such as bacteria in the blood (bacteremia, also known as septicemia). Although SIgMD was first described in two children, the disorder can occur in babies, children, and adults. It is characterized by isolated absence or deficiency of immunoglobulin M (IgM), normal levels of other immunoglobulins, and recurrent infections (especially by Staphylococcus aureus, Streptococcus pneumoniae, Hemophilus influenza). The cause is still unclear. The diagnosis includes isolated deficiency ofIgM in the blood and no other immunodeficiency or secondary cause of low IgM. Patients with SIgMD and recurrent infections are managed like other antibody defects and deficiencies. It is suggested that people with SIgMD have pneumococcal and meningococcal vaccines, people with SIgMD who have recurrent infections should have prophylactic antibiotics and immune globulin replacement. Also known as: selective IgM deficiency disease, selective immunoglobulin M deficiency.