This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Selective IgM deficiency (SIgMD) is a rare immune disorder in which a person has no immunoglobulin M (IgM) antibodies, or too little IgM, with normal levels of IgG and IgA antibodies. IgM is the first antibody the immune system makes to fight a new infection. Therefore, when a person does not have enough IgM, the body may have difficulty fighting infections. SIgMD can occur in infants, children, or adults. The disorder may occur as a primary disorder (on its own) or more commonly, as a secondary disorder (associated with another underlying disease or condition). SIgMD may occur in association with some cancers, autoimmune diseases, allergic diseases, and gastrointestinal diseases.
Symptoms of SIgMD may include repeated viral, bacterial, or fungal infections, such as ear infections, bronchitis, sinusitis, and pneumonia. Infections may be life-threatening. Repeated infections are common in infants with SIgMD. In some people, diarrhea or a skin rash is the first symptom. Others do not have symptoms specific to SIgMD and are diagnosed when being evaluated for another condition. The diagnosis is made by blood tests showing low or absent IgM and normal levels of other antibodies, as well as diagnosing or ruling out underlying conditions that can cause low levels of IgM.
The cause of SIgMD is still unclear. SIgMD usually occurs in only one person in a family, but familial cases have occasionally been reported. It may occur in some people with chromosome disorders such as 22q11.2 deletion syndrome.
There are no official treatment recommendations since information about SIgMD is limited. Treatment options depend on the severity of symptoms and whether a person has an associated underlying disease. Treatment may include prompt treatment of infections, taking measures to prevent infections, prophylactic antibiotics, and immune globulin therapy.
For more information, visit GARD.